Communication control method, communication node, and mobile node

ABSTRACT

A technique is disclosed in which an MN (mobile node)  100  notifies, to a CN (correspondent node), home network connection information indicative of whether or not it is currently in connection with a home network which has allocated its own plurality of HoAs (home addresses), an address of each HA (home agent) and an ID of each HA in a state associated with the plurality of HoAs. Based on the information received from the MN, the CN grasps the home network with which the MN is currently in connection and makes an inquiry about the condition of the HA and sets an appropriate HoA, judged on the basis of the grasping result or the inquiry result, as a destination address of a packet to be transmitted to the MN.

TECHNICAL FIELD

The present invention relates to a communication control method,communication node and mobile node which are designed to makecommunications through the use of the IP (Internet Protocol), and moreparticularly to a communication node such as a mobile node having both amultihome function and a mobile function, a correspondent node servingas a communication partner of this mobile node or a home agent designedto manage this mobile node, and a communication control method ofcontrolling communications between a mobile node and these communicationnodes.

BACKGROUND ART

So far, there has been known a configuration, referred to as a sitemultihome, which establishes connections with a plurality of internetservice providers (ISPs) and enables a subordinate's network to use aplurality of prefixes allocated from each of the ISPs. In addition,there has been known a configuration, referred to as a host multihome,which has a plurality of interfaces and acquires an address from aconnection-accepting side for each of the interfaces. In the followingdescription, a site having a side multihome configuration will bereferred to as a multihoming site while a subnet (sub-network)pertaining to the multihoming side will be referred to as a sitemultihoming network.

First of all, referring to FIG. 30, a description will be givenhereinbelow of a site multihome. FIG. 30 is an illustration of oneexample of a configuration of a network for explaining a site multihomeaccording to a prior art technique.

FIG. 30 shows a site 1 which has connections with a plurality of ISPs(ISP 1 and ISP 2) and maintains a connectivity to the internet 701,which is an IP network, through these ISPs. This site 1 includes asubnet A and a subnet B. Therefore, the site 1 is a multihoming site,and the subnets A and B are site multihoming networks.

The site multihome is a technology capable of multiplexing connectionroutes to the internet 701, and the utilization of the site multihomeallows the enhancement of the fault resistance characteristic on theconnectivity from a communication node 702 within the site 1 to theinternet 701. For example, the communication node 702 within the site 1can establish a connection with the internet 701 through two ISPs of theISPs 1 and 2 or it can make a connection through the internet 701 with acommunication partner (CN: Correspondent Node) 703.

A prefix (network prefix) is advertised from each of the ISP 1 and theISP 2 to the site 1 shown in FIG. 30 and, hence, the plurality ofprefixes are available within a subnet pertaining to the site 1. Thus,for example, the communication node 702 having a connection with thesubnet A can generate a plurality of addresses configured with of theprefixes of the respective ISP 1 and ISP 2.

As means whereby the communication node 702 gets the advantage based onthe site multihome, there is a method of switching addresses to be usedfor communications as needed. The effect based on the site multihome isrealizable by determining a transit ISP for a source address in the caseof a transmission packet and by determining a transit ISP for adestination address in the case of a reception packet.

On the other hand, at present, in the case of the IETF SHIM6, as a meanswhereby a communication node which is in a multihomed condition owing tothe site multihome makes a communication with a communication partnerthrough the use of a plurality of addresses, there has been proposed amethod of managing a plurality of addresses in the interior of a networklayer and mapping them into a single identifier with respect to an upperlayer for concealing the fact that the plurality of addresses exist (forexample, see the following Non-Patent Document 1).

When a communication node transmits a packet to a communication partnerby switching a source address, a need exists to previously notify aplurality of addresses to be used for the switching to the communicationpartner, and the Non-Patent Document 1 additionally discloses a messagefor the notification of the information thereon. As a method whereby acommunication partner can grasp a plurality of addresses of acommunication node which is a source, in addition to the method proposedby the Non-Patent Document 1, it is also acceptable to employ a methodin which the notification is made in a state where a plurality ofaddresses are included in a message according to a different protocol,such as a binding update message based on the mobile IP disclosed in thefollowing Non-Patent Document 2. Thus, the communication partner canrecognize that, even in the case of a packet in which a different sourceaddress is set, it is a packet transmitted from the same communicationnode.

Meanwhile, several methods are conceivable as means whereby acommunication partner determines a destination address to be set in atransmission packet. For example, there are a method of directly using,as a destination address, an address set in a source address of a packetreceived from a communication node which is in a multihoming conditionand a method which involves using an address indicated explicitly bythat communication node or using an address selected in consideration ofinformation on address selection.

Thus, as the advantages, the utilization of the site multihome enablesmultiplexing the communication routes at the transmission/reception of apacket and achieves the recovery at a communication disconnectionstemming from the interior of an ISP, the load distribution for the ISPor the like.

In the following description, a node which is in connection with a sitemultihoming network and which generates and holds a plurality ofaddresses configured with a plurality of prefixes (network prefixes)will sometimes be referred to as a site multihoming node.

Secondly, referring to FIG. 31, a description will be given hereinbelowof a host multihome. FIG. 31 is an illustration of one example of anarrangement of a network for explaining a host multihome according to aconventional technique. FIG. 31 shows a communication node 902 whichestablishes connections with subnets (subnet A and subnet B) through theuse of a plurality of interfaces and maintains the connectivity with theinternet 901 which is an IP network.

In this case, the host multihome signifies a configuration in which anode (which is sometimes referred to as a host multihoming node) havinga plurality of interfaces holds a plurality of addresses acquired fromeach interface connection side. Anode (for example, the communicationnode 902) having such a configuration can multiplex the communicationroutes at the transmission/reception of a packet as well as the sitemultihome in a manner such that the switching among the interfaces ismade for the communication with the communication partner 903, and itcan provide the advantages, such as the recovery at communicationdisconnection stemming from interfaces, connected networks and ISPs andthe load distribution.

Furthermore, a brief description will be given hereinbelow of a mobileIP disclosed in the Non-Patent Document 2. An MN (Mobile Node) which isa communication node according to the mobile IP receives, as allocation,at least one HoA (Home Address) from its own home network. In a case inwhich this MN moves to a different sub-network (foreign network), itacquires at least one CoA (Care-of Address) on a sub-network of thedriving destination and transmits a binding update message including CoAassociation information as binding information indicative of therelationship between this CoA and the HoA allocated in the home networkto an HA (Home Agent) in the home network. In this way, the HA receives,as proxy, a packet transmitted toward the HoA of the MN and transfers itto the CoA, which enables the MN to receive the packet addressed to theHoA even in the case of lying in a foreign network.

Moreover, in a case in which the MN has established a connection with ahome network, it transmits a binding update message to an HA in thishome network for making a request for the deletion of the registered CoAassociation information. Upon receipt of this binding update message,the HA deletes the CoA association information on the MN, it holds, andstops the proxy reception of a packet transmitted toward the HoA of theMN. In this way, the packet addressed to the HoA of the MN is receivedby the interface of the MN which is in connection with the home network.

A description will be given hereinbelow of a case in which a pluralityof HAs have relation with an MN. As the case in which a plurality of HAshave relation with an MN, the following two cases are conceivable.

The first is a case in which a plurality of HAs exists in a home networkallocated to an MN. In this case, each of the plurality of HAs isconnected on the same linkage, and the MN registers the CoA associationinformation in one of these HAs. As disclosed in the Non-Patent Document1, the MN can acquire an address list of the HAs existing in the homenetwork by employing a technique referred to as a DHAAD (Dynamic HomeAgent Address Discovery). This technique is realizable in a manner suchthat the MN first transmits a request message to a home agent anycastaddress generated with a prefix of its own home network and, uponreceipt of this request message, the HA in the home network returns aresponse message including an address list of the HAs to this MN. Theaddresses of the HAs included in the address list are arranged in theorder of the priority of the respective HAs and, hence, the MN canselect the appropriate HA by using the addresses in the order from theleading address.

The second is a case in which a plurality of home networks are allocatedto an MN. The home network to be allocated to the MN is a network whichprovides an HoA of the MN and an HA made to manage this HoA, and theallocation of the plurality of home networks signifies that, since anHoA is allocated from each of the home networks, the MN holds aplurality of HoAs at the same time and an HA made to manage each of theHoAs exists on each of the home networks. As well as a communicationnode which is in a site multihomed condition, this MN is required toselect an HoA to be set in a source address of a transmission packet,and when the MN switches the HoA as the source address to transmit apacket to a CN, it is required to notify a plurality of HoAs, which areto be used for the switching, to this CN in advance. In the second case,as well as the first case, a plurality of HAs can exist in a homenetwork.

In addition, in a case in which an MN after movement transmits a packetto a CN without carrying out a route optimization, the MN generates apacket where its own HoA is set as a source address and transmits it ina state where it is encapsulated as an inner packet into an outer headeraddressed to the HA. Thus, the packet is delivered to the HA in aencapsulated condition and, after decapsulated in the HA, it istransferred to the CN. As disclosed in the Non-Patent Document 2, thedestination of the outer header of this encapsulated packet should bethe address of the HA which is managing the HoA set in the sourceaddress of the inner header. Therefore, in the case of an MN having aplurality of HoAs, since the HA through which the encapsulated packetpasses is determined according to which of HoAs is selected as a sourceaddress of the inner packet, it is appropriate that the HoA selection ismade in consideration of the condition of each of the HAs.

In a case in which a plurality of home networks allocated to an MN existunder the same management, although the MN may acquire priorityinformation produced with respect to all the HAs existing on a pluralityof home networks as the objects of comparison at a time, if a pluralityof home networks which are not under the same management are allocatedthereto, difficulty is experienced in acquiring the priorityinformation, which has been produced with all the HAs being the objectsof comparison, at a time, and the MN itself is required to collect theinformation from each of the HAs on a plurality of home networks formaking the comparison therebetween. For this reason, for acquiring theinformation for the comparison between HAs existing on the respectivehome networks, the MN is required to inquire at the HAs on therespective home networks allocated thereto.

On the other hand, as in the case of the CN which is a communicationnode in a multihomed condition, as means whereby a CN determines adestination address to be set in a transmission packet, several methodsare conceivable. For example, there are a method in which an HoA set ina source address of a packet received from an MN is directly used as adestination address and a method which involves using an addressexplicitly indicated by the MN or using an HoA selected in considerationof information on address selection.

In a case in which a CN transmits a packet to an MN, since the CN doesnot know the CoA of this MN, the CN transmits a packet in a state wherean HoA is set as a destination address. The packet where the HoA of theMN is set as the destination address is proxy-received by an HA managingthis HoA, and the HA encapsulates it and transmits toward the CoA of theMN. Thus, as well as a packet to be transmitted by the MN, the HAthrough which the packet transmitted from the CN passes becomes an HAwhich manages the HoA set as a destination address of a transmissionpacket and, hence, it is appropriate to select a destination address ofthe transmission packet to the MN in consideration of the HA condition.Moreover, in this case, as well as the case of the MN, there is a needfor the CN to make an inquiry at an HA existing in a home network of theMN so as to acquire the information for the comparison between the HAs.

A description will be given hereinbelow of a case in which a homenetwork to be allocated to an MN is a site multihoming network. The HoAof the MN is an address configured with a prefix advertised in anetwork. Therefore, in a case in which the home network is a sitemultihoming network, since a plurality of different prefixes areadvertised in the home network, if a plurality of different prefixes ina single network are available as prefixes for the configuration of theHoA of the MN, a single home network becomes capable of allocating aplurality of HoAs to a single MN.

As well as the case of the allocation of a plurality of home networks,also in this case, the MN is required to select an HoA to be set in asource address, and the CN is also required to select an HoA to be setas a destination address. In addition, conceivable is a case in which aplurality of home networks are allocated to an MN and, of these homenetworks, one or a plurality of home networks are site multihomingnetworks. Also in this case, it is considered that the destinationaddress selection is made by the MN and CN in a manner similar to thosementioned above.

Furthermore, a description will be given hereinbelow of a case in whichan MN according to the mobile IP is a host multihoming node. Asspecified in the mobile IP, a home network and a foreign network existas the connection-accepting side of an interface of the MN. This alsoapplies to a case in which a plurality of interfaces exist, and each ofthe interfaces is connectable to one of the networks.

In a case in which the MN makes communications through the use of aninterface which is in connection with the home network, since a homeaddress is allocated to this interface, a communication using an HoAdirectly becomes feasible without utilizing the packet switchingaccording to the mobile IP. On the other hand, if the MN makescommunications through the use of an interface which is in connectionwith a foreign network, since a CoA which is a valid address on theforeign network is allocated to this interface, employable are a methodof utilizing the mobile IP and encapsulating a packet using an HoAbetween an MN and an HA before the transmission/reception thereof, amethod of carrying out the route optimization with respect to a CN andconducting the transmission/reception by using a CoA directly, and othermanners.

-   Non-Patent Document 1: Erik Nordmark, Marcelo Bagnulo, “Multihoming    L3 Shim Approach”, draft-ietf-multi6-13shim-00.txt, 10 Jan. 2005.-   Non-Patent Document 2: Johnson, D. B., Perkins, C. E., and Arkko,    J., “Mobility Support in IPv6”, RFC3775, June 2004.

However, in a case in which, even after an MN holding a plurality ofHoAs has acquired a CoA to be associated with an HoA due to movement,for preventing the present position from being known, ittransmits/receives all packets through an HA without notifying the CoAacquired at the movement destination to a CN, the CN cannot grasp thepresent connection situation of the MN (for example, whether or not theMN is moving). As disclosed in the Non-Patent Document 2, this isbecause the registration of binding information in the CN by the MN ismade at its option.

For this reason, even in a situation where the MN is in connection withone of a plurality of home networks and is capable of directly making acommunication by using an HoA allocated from this home network, there isa possibility that the CN selects an HoA allocated from a home networkwhich is not in connection with the MN and starts the communication. Inthis case, a packet transmitted from the CN arrives at the MN through ahome network different from the home network which is in connection withthe MN, which creates a problem in that the packet transmission routebecomes relatively long and a delay of the packet transmission/receptionoccurs.

In addition, when the MN has a plurality of interfaces and one of theseinterfaces is in connection with a home network, the communicationbecomes feasible by directly using an HoA allocated to the interfacewhich is in connection with that home network. However, in a case inwhich, for utilizing a different interface connected to a foreignnetwork, the address allocated to this interface is registered in an HAin a state associated as a CoA with an HoA allocated to the interfacewhich is in connection with the home network, this CoA associationinformation is held in a binding cache of the HA, and all packetstransmitted to the HoA of the MN are proxy-received by the HA andtransferred to the associated CoA. Moreover, likewise, also with respectto the CN, in a case in which the MN associates an address, allocated toa different interface which is in connection with the foreign network,as a CoA with an HoA allocated to an interface which is in connectionwith the home network and registers it in the CN, this CoA associationinformation is held in a binding cache of the CN, and a packettransmitted from the CN to the HoA of the MN is delivered through the HAto the MN. This creates a problem in that, for the optimization of thecommunication route, the CN selects one to be transmitted to the CoA ofthe MN by use of the CoA association information.

Still additionally, since the interface connected to the home network isutilized when the CoA association information relative to the HoA isalready held in the HA and/or CN as the CoA association information onthe interface connected to the foreign network, if the CoA associationinformation in the HA and/or the CN are deleted, all the packets arereceived by the interface connected to the home network of the MN.

For these reasons, even in a case in which communications are made byusing both an interface connected to a home network and an interfaceconnected to a foreign network, a current-status binding update messageor a binding cache held by an HA and/or a CN cannot cope with thenotification and maintenance of these states, the MN cannot establish acommunication using simultaneously both the interface connected to thehome network and the interface connected to the foreign network. Inaddition, in this case, since the MN has registered the CoA associationinformation in the CN, this causes that the CN has an interpretationdifferent from the actual condition, i.e., the CN makes a judgment thatno connection with the home network takes place.

In a case in which a plurality of home networks are allocated to an MNand a CN selects an HoA in consideration of a condition of an HA of theMN when one or a plurality of home networks of these home networks aresite multihoming networks, even if a plurality of HoAs are notified fromthe MN, the CN cannot distinguish between these HoAs being addresses inthe home networks which are site multihoming networks and they beingaddresses in normal home networks. Accordingly, even if several HoAs ofthe plurality of HoAs allocated to the MN are allocated from the samehome network and managed by the same HA, the CN cannot recognize thisfact and, hence, there is a possibility that the CN makes a judgmentthat each of the HoAs is allocated from a separate home network andmanaged by a separate HA and makes an inquiry at the HA.

In this case, since the CN recognizes that the HAs equal in number tothe HaAs of the MN exist, for example, in the case of an inquiry at theHA, the inquiry is made at the HA which is recognized as the HAcorresponding to each HoA. Accordingly, the CN carries out unnecessaryinquiry, such as making the same inquiry at the same HA a number oftimes, which creates a problem in that ineffective time and processingtake place until the address selection reaches completion.

As described above, for the selection of an HoA of an MN by a CN, the CNcannot grasp the current MN connection condition and HoA allocationstatus, which creates a problem in that a delay of communication occursdue to undesirable HoA selection, unnecessary HA inquiry processing, orthe like.

Moreover, in a case in which an MN holds a plurality of interfaces andone of these interfaces is connected to a home network while a differentinterface is connected to a foreign network, there is a problem in that,even if both the interface connected to the home network and theinterface connected to the foreign network are available, the MN cannotutilize these at the same time on the basis of the mobile IP in thepresent situation.

BRIEF SUMMARY

In consideration of the above-mentioned problems, it is an object of thepresent invention to, when a plurality of HAs are allocated to an MN,enable a CN which is a communication partner of the MN to appropriatelyrecognize the HAs and connection condition of the MN and select anappropriate HoA from a plurality of HoAs and set it as a destinationaddress of a packet to be transmitted to the MN, thereby reducing thedelay stemming from the processing on selection among the plurality ofHoAs and the delay of communication due to a result of the selection forachieving the improvement of communication efficiency.

Furthermore, it is an object of the present invention to, even in a casein which an MN having a plurality of interfaces is connected to a homenetwork and a foreign network, enable an HA of the MN and/or a CN torecognize an appropriate connection condition of the MN, and allow theMN to employ these interfaces simultaneously for realizing themultiplexing of communication routes.

For achieving the above-mentioned purposes, in a communication controlmethod according to the present invention for a communication between amobile node to which a plurality of home addresses are allocated and apredetermined communication node, the mobile node notifies, to thepredetermined communication node, information enabling a selection of ahome address which is preferably set as a destination address of apacket when the packet is transmitted from the predeterminedcommunication node to the mobile node.

With this arrangement, when an MN has a plurality of HoAs, a CN which isa communication partner of the MN can select an appropriate HoA from theplurality of HoAs and set it as a destination address of a packet to betransmitted to the MN, thereby reducing the delay stemming from theprocessing on selection among the plurality of HoAs and the delay ofcommunication due to a result of the selection for achieving theimprovement of communication efficiency.

Combined with the above-mentioned arrangement, the communication controlmethod according to the present invention comprises:

a mobility association information notifying step in which the mobilenode notifies, to the predetermined communication node, information onassociation between the plurality of home addresses of the mobile nodeand home network connection information indicative of whether or not themobile node is currently in connection with one or a plurality of homenetworks which have allocated the plurality of home addresses;

a home address specifying step in which, when the predeterminedcommunication node transmits a packet to the mobile node, thepredetermined communication node makes reference to the home networkconnection information to specify a home network with which the mobilenode is currently in connection; and

a destination address setting step in which the communication node setsthe home address of the mobile node, associated with the home networkspecified in the home address specifying step, as a destination addressof the packet.

With this arrangement, when the MN is in connection with a home network,the CN can transmit a packet in which set is an HoA which allows thedirect arrival at this home network.

In addition, combined with the above-mentioned arrangement, thecommunication control method according to the present invention furthercomprises a care-of-address acquiring step in which, when the mobilenode is currently in connection with one or a plurality of home networkswhich have allocated the plurality of home addresses, the mobile nodeacquires a care-of address compatible with the home network,

wherein, in the mobility association information notifying step, thecare-of address acquired in the care-of-address acquiring step is usedas the home network connection information.

With this arrangement, through the notification of the care-of addressacquired in the home network, the mobile node can notify the fact thatan interface having the home address corresponding to this care-ofaddress is currently in connection with the home network.

Still additionally, combined with the above-mentioned arrangement, thecommunication control method according to the present invention furthercomprises:

a mobility association information notifying step in which the mobilenode notifies, to the predetermined communication node, information onthe association among the plurality of home addresses of the mobilenode, addresses of one or a plurality of home agents managing theplurality of home addresses and home agent ID information enabling theidentification of each of the plurality of home agents;

a home agent inquiring step in which the predetermined communicationnode makes an inquiry at each of the plurality of home agents,identified by the home agent ID information, about a condition of thehome agent;

a home agent selecting step in which the predetermined communicationnode selects a home agent, through which a packet to be transmitted fromthe predetermined communication node to the mobile node passes, on thebasis of a result of the inquiry in the home agent inquiring step; and

a destination address setting step in which the home address of themobile node associated with the home agent selected in the home agentselecting step is set as the packet destination address.

This arrangement allows the CN to make an inquiry about the conditionsat the HAs which are made to manage a plurality of HoAs of the MN toselect an optimum HA through which a packet to be transmitted from theCN to the MN passes and to transmit the packet in which the HoAassociated with this HA is set. Moreover, at this time, this arrangementenables avoiding the duplicate inquiry at the same HA.

Yet additionally, combined with the above-mentioned arrangement, thecommunication control method according to the present invention furthercomprises:

a mobility association information notifying step in which, when themobile node has a plurality of communication interfaces each connectableto a different network and is connected to a home network through atleast one of the plurality of communication interfaces, the mobile nodenotifies, to the predetermined communication node, information onassociation between home network connection information indicative ofthe home address which is currently in connection with the home networkand the fact that this home address is currently in connection with thehome network and an address allocated to a different communicationinterface which is not connected to the home network; and

an destination address setting step in which, when the predeterminedcommunication node transmits a packet to the mobile node, thepredetermined communication node selects and sets a destination addressto be set as a destination address of the packet, from the home addresswhich is currently in connection with the home network and the addressallocated to the different communication interface.

With this arrangement, when the CN or the HA acquires each addressallocated to each of the plurality of communication interfaces of theMN, for example, if a disconnection of a communication using an HoA as adestination address occurs, the selection of a CoA associated with thisHoA is made, which enables the recovery of the communication in a mannersuch that the packet in which the HoA is set as the destination addressis switched to be directed to the CoA associated with the HoA.

Moreover, combined with the above-mentioned arrangement, thecommunication control method according to the present invention furthercomprises a selection function notifying step in which the predeterminedcommunication node notifies the fact that the predeterminedcommunication node has a home address selection function to select thehome address properly set as a destination address of a packet when thepacket is transmitted from the predetermined communication node to themobile node.

This arrangement allows the CN or the HA to notify, to the MN, the factthat it has a function (function according to the present invention) tobe used when it selects a home address, including, for example, a homenetwork connection information registration function and others.

Still moreover, combined with the above-mentioned arrangement, in thecommunication control method according to the present invention, thepredetermined communication node is a home agent of the mobile node and,in the selection function notifying step, the predeterminedcommunication node transmits a router advertisement message includinginformation indicating that the predetermined communication node has thehome address selection function so as to notify the fact that thepredetermined communication node has the home address selectionfunction, to the mobile node connected to a network in which thepredetermined communication node exists.

This arrangement allows the HA to transmit, for example, a routeradvertisement message, in which set is a flag indicative of the factthat it handles a function according to the present invention, to the MNconnected to the home network, thereby achieving the notification of thefact that it handles a function of the present invention.

Furthermore, for achieving the above-mentioned purposes, a communicationnode according to the present invention, which makes a communicationwith a mobile node to which a plurality of home addresses are allocated,comprises:

mobility association information acquiring means for receiving, from themobile node, information on the association between the plurality ofhome addresses of the mobile node and home network connectioninformation indicative of whether or not the mobile node is currently inconnection with one or a plurality of home networks which have allocatedthe plurality of home addresses;

home address specifying means for, when a packet is transmitted to themobile node, making reference to the home network connection informationto specify a home network with which the mobile node is currently inconnection; and

destination address setting means for setting the home address of themobile node, associated with the home network specified by the homeaddress specifying means, as a destination address of the packet.

With this configuration, when the MN is in connection with a homenetwork, the CN can transmit a packet in which set is an HoA whichallows the direct arrival at this home network.

Furthermore, for achieving the above-mentioned purposes, a communicationnode according to the present invention, which makes a communicationwith a mobile node to which a plurality of home addresses are allocated,comprises:

mobility association information acquiring means for notifying, from themobile node, information on association among the plurality of homeaddresses of the mobile node, addresses of one or a plurality of homeagents managing the plurality of home addresses and home agent IDinformation enabling an identification of each of the plurality of homeagents;

home agent inquiry executing means for, when a packet is transmitted tothe mobile node, making an inquiry at each of the plurality of homeagents identified on the basis of the home agent ID information about acondition of the home agent;

home agent selecting means for selecting a home agent, through which apacket to be transmitted to the mobile node passes, on the basis of aresult of the inquiry acquired by the home agent inquiry executingmeans; and

destination address setting means for setting the home address of themobile node, associated with the home agent selected by the home agentselecting means, as a destination address of the packet.

This configuration allows the CN to make an inquiry about the conditionsat the HAs which are made to manage a plurality of HoAs of the MN toselect an optimum HA through which a packet to be transmitted from theCN to the MN passes and to transmit the packet in which the HoAassociated with this HA is set. Moreover, at this time, thisconfiguration enables avoiding the duplicate inquiry at the same HA.

Still furthermore, for achieving the above-mentioned purposes, acommunication node according to the present invention, which makes acommunication with a mobile node to which one or a plurality of homeaddresses are allocated, with the mobile node having one or a pluralityof communication interfaces connectable to a home network and a foreignnetwork and the mobile node being connected to the home network throughat least one of the one or plurality of communication interfaces,comprises:

mobility association information acquiring means for receiving, from themobile node, information on the association between home networkconnection information indicative of the current connection with thehome network and an address allocated to a different communicationinterface which is not in connection with the home network; and

destination address setting means for, when a packet is transmitted tothe mobile node, selecting and setting a destination address, as adestination address of the packet, from the home address which iscurrently in connection with the home network and the address allocatedto the different communication interface.

With this configuration, when the CN or the HA acquires each addressallocated to each of the plurality of communication interfaces of theMN, for example, if a disconnection of a communication using an HoA as adestination address occurs, the selection of a CoA associated with thisHoA is made, which enables the recovery of the communication in a mannersuch that the packet in which the HoA is set as the destination addressis switched to be directed to the CoA associated with the HoA.

In addition, combined with the above-mentioned configuration, in thecommunication node according to the present invention, a care-of addressacquired in the home network with which the mobile node is currently inconnection is used as the home network connection information indicativeof the current connection with the home network.

With this configuration, for example, by detecting the fact that acare-of address notified from a mobile node and a home addresscorresponding to this care-of address have the same network prefix, thecommunication node can grasp the fact that the interface having thishome address is currently in connection with the home network.

Yet furthermore, for achieving the above-mentioned purposes, a mobilenode according to the present invention to which one or a plurality ofhome addresses are allocated, comprises mobility association informationnotifying means for notifying, to a predetermined communication node,home network connection information indicative of whether or not its owncommunication interface is currently in connection with one or aplurality of home networks which have allocated the home addresses.

With this configuration, an MN can notify, to a CN, informationindicative of whether or not the MN is in connection with a home networkand indicative of the home network connected thereto and, when the MN isin connection with the home network, the CN can transmit a packet inwhich set is an HoA which allows the direct arrival at this homenetwork.

Moreover, for achieving the above-mentioned purposes, a mobile nodeaccording to the present invention to which a plurality of homeaddresses are allocated, comprises mobility association informationnotifying means for notifying, to a predetermined communication node,information on the association among its own plurality of homeaddresses, addresses of one or a plurality of home agents managing theplurality of home addresses and home agent ID information enabling theidentification of each of the plurality of home agents.

This configuration allows the MN to notify, to the CN, information onthe home agents managing its own plurality of HoAs and further the CN tomake an inquiry about the conditions at the HAs which are made to managethe plurality of HoAs of the MN to select an optimum HA through which apacket to be transmitted from the CN to the MN passes and to transmitthe packet in which the HoA associated with this HA is set. At thistime, add to it that this configuration enables avoiding the duplicateinquiry at the same HA.

Still moreover, for achieving the above-mentioned purposes, a mobilenode according to the present invention to which one or a plurality ofhome addresses are allocated, with the mobile node having one or aplurality of communication interfaces connectable to a home network anda foreign network and the mobile node being connected to the homenetwork through at least one of the one or plurality of communicationinterfaces, comprises mobility association information notifying meansfor notifying, to a predetermined communication node, information on theassociation between home network connection information indicative ofthe current connection with the home network and an address allocated toa different communication interface which is not in connection with thehome network.

With this configuration, the MN can notify, to the CN or the HA, eachaddress allocated to each of the plurality of communication interfacesof the MN, for example, if a disconnection of a communication using anHoA as a destination address occurs, the CN or the HA selects a CoAassociated with this HoA, which enables the recovery of thecommunication in a manner such that the packet in which the HoA is setas the destination address is switched to be directed to the CoAassociated with the HoA.

In addition, combined with the above-mentioned configuration, the mobilenode according to the present invention further comprisescare-of-address acquiring means for acquiring a care-of addresscompatible with the home network with which the mobile node is currentlyin connection,

wherein the mobility association information notifying means uses thecare-of address, acquired by the care-of-address acquiring means, as thehome network connection information.

With this configuration, through the notification of the care-of addressacquired in the home network, the mobile node can notify the fact thatan interface having the home address corresponding to this care-ofaddress is currently in connection with the home network.

According to the present invention, as the advantages based upon withthe above-mentioned arrangements and configurations, an MN having aplurality of HoAs notifies, to a CN, a connection condition with anetwork corresponding to each of the plurality of HoAs, so the CNbecomes capable of selecting an appropriate HoA, and even in a case inwhich several HoAs of the plurality of the MN are managed by the sameHA, the notification of appropriate information to the CN enables the CNto select an appropriate HoA and allows an efficient inquiry at an HA.

In addition, since the MN notifies, to the HA and/or the CN, informationon an interface connected to a network as information separate from CoAassociation information on a different interface, the HA and/or the CNcan recognize a proper connection condition of the MN, and the MN canuse simultaneously an interface connected to a home network and aninterface connected to a foreign network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one example of a configuration of a networkaccording to a first embodiment of the present invention;

FIG. 2 is a block diagram showing one example of a configuration of anMN according to the first embodiment of the present invention;

FIG. 3 is an illustration of one example of an information storage tablestoring mobility association information in an allocation mobilityassociation information holding unit of an MN according to the firstembodiment of the present invention;

FIG. 4 is an illustration of one example of information which is to behanded over from a connected network judging unit to a notified HoAinformation holding unit and a plural-HoA information notificationmessage generating unit in an MN according to the first embodiment ofthe present invention;

FIG. 5 is an illustration of one example of HoA information included ina plural-HoA information notification message generated by a plural-HoAinformation notification message generating unit of an MN according tothe first embodiment of the present invention;

FIG. 6 is a block diagram showing one example of a configuration of acommunication partner according to the first embodiment of the presentinvention;

FIG. 7 is an illustration of a first example of a configuration of anetwork according to second and third embodiments of the presentinvention;

FIG. 8 is a block diagram showing one example of a configuration of anMN according to the second embodiment of the present invention:

FIG. 9A is an illustration of a first example of in-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe second embodiment of the present invention;

FIG. 9B is an illustration of a second example of in-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe second embodiment of the present invention;

FIG. 9C is an illustration of a first example of non-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe second embodiment of the present invention;

FIG. 9D is an illustration of a second example of non-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe second embodiment of the present invention;

FIG. 10 is an illustration of a second example of a configuration of anetwork according to the second and third embodiments of the presentinvention;

FIG. 11 is an illustration of a first example of a configuration of abinding information notification message to be generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 12 is an illustration of a second example of a configuration of abinding information notification message to be generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 13 is an illustration of a third example of a configuration of abinding information notification message to be generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 14 is an illustration of a first example of a binding informationnotification message including an alternate CoA, generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 15 is an illustration of a second example of a binding informationnotification message including an alternate CoA, generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 16 is an illustration of a third example of a binding informationnotification message including an alternate CoA, generated by a bindinginformation notification message generating unit of an MN according tothe second embodiment of the present invention;

FIG. 17 is a block diagram showing one example of a configuration of anHA according to the second embodiment of the present invention;

FIG. 18 is a block diagram showing one example of a configuration of aCN according to the second embodiment of the present invention;

FIG. 19 is a block diagram showing one example of a configuration of anMN according to the third embodiment of the present invention;

FIG. 20 is an illustration of a first example of a configuration of abinding information notification message including a home CoA, generatedby a binding information notification message generating unit of an MNaccording to the third embodiment of the present invention;

FIG. 21 is an illustration of a second example of a configuration of abinding information notification message including a home CoA, generatedby a binding information notification message generating unit of an MNaccording to the third embodiment of the present invention;

FIG. 22 is an illustration of a third example of a configuration of abinding information notification message including a home CoA, generatedby a binding information notification message generating unit of an MNaccording to the third embodiment of the present invention;

FIG. 23 is an illustration of a fourth example of a configuration of abinding information notification message including a home CoA, generatedby a binding information notification message generating unit of an MNaccording to the third embodiment of the present invention;

FIG. 24 is an illustration of a fifth example of a configuration of abinding information notification message including a home CoA, generatedby a binding information notification message generating unit of an MNaccording to the third embodiment of the present invention;

FIG. 25 is an illustration of a first example of a configuration of abinding information notification message including a foreign CoA,generated by a binding information notification message generating unitof an MN according to the third embodiment of the present invention;

FIG. 26 is an illustration of a second example of a configuration of abinding information notification message including a foreign CoA,generated by a binding information notification message generating unitof an MN according to the third embodiment of the present invention;

FIG. 27A is an illustration of a first example of in-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe third embodiment of the present invention;

FIG. 27B is an illustration of a second example of in-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe third embodiment of the present invention;

FIG. 27C is an illustration of a first example of non-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe third embodiment of the present invention;

FIG. 27D is an illustration of a second example of non-connectioninformation which is to be handed over from a connected network judgingunit to a notified HoA information holding unit and a bindinginformation notification message generating unit in an MN according tothe third embodiment of the present invention;

FIG. 28 is a block diagram showing one example of a configuration of anHA according to the third embodiment of the present invention;

FIG. 29 is a block diagram showing one example of a configuration of aCN according to the third embodiment of the present invention;

FIG. 30 is an illustration of one example of a configuration of anetwork for explaining a site multihome according to a conventionaltechnique; and

FIG. 31 is an illustration of one example of a configuration of anetwork for explaining a site multihome according to a conventionaltechnique.

DETAILED DESCRIPTION

First to third embodiments of the present invention will be describedhereinbelow with reference to the drawings.

First Embodiment

First of all, referring to FIG. 1, a description will be given of aconfiguration of a network according to a first embodiment of thepresent invention. FIG. 1 is an illustration of one example of aconfiguration of a network according to the first embodiment of thepresent invention. Incidentally, the configuration of a communicationsystem shown in FIG. 1 is only one example, but the present invention isnot limited to the configuration shown in FIG. 1.

In FIG. 1, shown are four sites (site 1, site 2, site 3 and site 4), anMN 100 connected to a network of the site 2 of these four sites and a CN150 connected to a network of the site 4. Moreover, the respective sites1 to 4 are connected through ISPs to each other. The site 1 is connectedthrough the ISP 1 to the internet 110, the site 2 is connected theretothrough the ISP 2 and the ISP 3, the site 3 is connected thereto throughthe ISP 4, and the site 4 is connected thereto through the ISP 5.

To the MN 100, a home network 1, a home network 2 and a home network 3are allocated from the site 1, the site 2 and the site 3, respectively,and an HA 1 serving as a home agent made to manage the MN 100 exists inthe home network 1, and an HA 2 and an HA 3 lie in the home network 2and the home network 3, respectively. The home network 2 pertains to thesite 2 connected to two ISPs (ISP 2 and ISP 3) so as to have a sitemultihome configuration, and since two prefixes (network prefixes)advertised from both the ISP 2 and the ISP 3 are usable within the homenetwork 2, the home network 2 can allocate a global address (HoA),configured with these two prefixes, to the MN 100.

On the other hand, since only one prefix advertised from one ISP isavailable within each of the home network 1 and the home network 3, oneHoA is allocated to the MN 100 within each of the home network 1 and thehome network 3. Although a plurality of addresses can also be generatedwith one prefix, a description will be given hereinbelow of a case inwhich one global address is generated from one prefix. Each of theseglobal addresses will sometimes be referred to simply as an address.Moreover, the configuration shown in FIG. 1 is only one example, and thenumbers of home networks to be allocated to the MN 100, home agents,HoAs and interfaces of the MN 100 are not limited to the above-mentionedconfiguration, but one or multiple is also acceptable.

In the following description, a prefix advertised from each of the ISPs1 to 5 is expressed by a symbol in which the number of the ISP isappended to PF. That is, the prefix advertised from the ISP 1 isexpressed by PF1, the prefix advertised from the ISP 2 is designated byPF1, the prefix advertised from the ISP 3 is represented by PF3, theprefix advertised from the ISP 4 is depicted by PF4, and the prefixadvertised from the ISP 5 is denoted by PF5.

For making clear the prefix of an address held by the MN 100 and thecontents (HoA or CoA) of this address, an address held by the MN 100 isexpressed by a combination of a symbol where the number of ISP isappended to PF and HoA or CoA. That is, for example, an HoA configuredwith a prefix advertised from the site 1 is designated by PF1. HoA.Accordingly, HoAs held by the MN 100 in FIG. 1 are four: PF1. HoA, PF2.HoA, PF3. HoA and PF4. HoA, while CoAs acquired from a foreign network 1under connection are two: PF2. CoA and PF3. CoA. Moreover, an address ofthe CN 150 is depicted by PF5. CN.

With the network configuration shown in FIG. 1, a first embodiment ofthe present invention will be described hereinbelow in consideration ofa case in which, when the MN 100 is in connection with the foreignnetwork 1, the MN 100 makes a communication with the CN 150 through theHA 1 within the home network 1. Thus, in this case, a packet to betransmitted from the MN 100 to the CN 150 includes a packet addressed tothe CN 150 as an inner packet and becomes an encapsulated packetaddressed to the HA 1 within the home network 1.

First, a description will be given of a configuration of an MN accordingto the first embodiment of the present invention. FIG. 2 is a blockdiagram showing one example of a configuration of an MN according to thefirst embodiment of the present invention. The MN 100 shown in FIG. 2 iscomposed of a transmission/reception unit 201, an IP address acquiringunit 202, an allocation mobility association information holding unit203, a connected network judging unit 204, a notified HoA informationholding unit 205 and a plural-HoA information notification messagegenerating unit 206. In FIG. 2, although functions realized in the MN100 are shown by blocks, these functions are realizable by hardware orsoftware.

The transmission/reception unit 201 is connected through radiocommunication to a network (for example, a home network of the MN 100 ora foreign network), and it fulfills a function to make a communicationwith an arbitrary node within these networks and to make a communicationthrough an ISP with an arbitrary node connected to a different network.This transmission/reception unit 201 includes one or more communicationinterfaces, and an IP address generated/acquired by the IP addressacquiring unit 202 is allocated to each of these communicationinterfaces.

Moreover, the IP address acquiring unit 202 fulfills a function togenerate or acquire an IP address through the use of the addressautomatic setting (stateless address autoconfiguration), the DHCP(Dynamic Host Configuration Protocol), the manual setting or the likefor the purpose of obtaining a valid IP address in a network connectedthereto. Still moreover, for example, a case in which an address isdynamically allocated from an operator side in a manner different fromthe DHCP is also conceivable.

For example, in the case of the employment of the address automaticsetting, the IP address acquiring unit 202 hands over a prefix,advertised in a connected network, to the connected network judging unit204 to indicate the judgment on the connected network on the basis ofthis prefix. If the judgment result by the connected network judgingunit 204 shows a connection with a foreign network, the IP addressacquiring unit 202 automatically generates an address by use of a prefixacquired in advance. On the other hand, if the judgment result shows aconnection with a home network, the IP address acquiring unit 202acquires a home address, allocated from a connected home network, fromthe allocation mobility association information holding unit 203 toallocate this address to a communication interface or automaticallygenerates an address by use of a prefix in a home network to allocate itto a communication interface. An IP address acquired by the IP addressacquiring unit 202 in this way is allocated to a communication interfaceof the transmission/reception unit 201 in a state associated.Incidentally, the acquisition of the prefix information on aconnection-accepting side network and the address generation/acquisitionmethod are not limited to the above-mentioned methods.

In addition, the allocation mobility association information holdingunit 203 has a function to hold a home network allocated thereto, an HoAallocated from this home network, a prefix thereof, information (forexample, address of an HA) on an HA managing this HoA and others in astate associated with each other.

Still additionally, the connected network judging unit 204 has afunction to make a judgment on a network with which it is in connection.The connected network judging unit 204 acquires a prefix of its own homenetwork from the allocation mobility association information holdingunit 203 so as to make a comparison between this acquired prefix and aprefix in the connected network notified from the IP address acquiringunit 202. When this comparison result shows that both the prefixes agreewith each other, a judgment is made that it is in connection with thehome network. If they do not agree with each other, a judgment is madethat it is in connection with a foreign network. The connected networkjudging unit 204 hands over this judgment result to the IP addressacquiring unit 202. The method of making a judgment on a connectednetwork is not limited to the above-mentioned method, but an arbitrarymethod whereby a variation of a connected network is detectable isusable.

Yet additionally, when the connected network judging unit 204 hasdetected a connection with a different network due to the movement ofthe MN 100, the connected network judging unit 204 hands over, to thenotified HoA information holding unit 205, the information indicative ofwhether the connection-accepting side network is the home network or theforeign network, a plurality of HoAs to be notified to the CN 150 andthe information (for example, an address of the HA) on the HA which hasallocated these HoAs, acquired from the allocation mobility associationinformation holding unit 203, and indicates the holding of these piecesof information, and further hands them over to the plural-HoAinformation notification message generating unit 206 and gives aninstruction to the plural-HoA information notification messagegenerating unit 206 for generating a plural-HoA information notificationmessage.

The notified HoA information holding unit 205 fulfills a function tohold the information on plural-HoA information handed over from theconnected network judging unit 204 and notified to the CN 150. Moreover,the plural-HoA information notification message generating unit 206generates a plural-HoA information notification message on the basis ofthe information notified from the connected network judging unit 204 andhands over this plural-HoA information notification message to thetransmission/reception unit 201 and gives an instruction for thetransmission thereof to the CN 150.

Referring to FIG. 3, a description will be given hereinbelow ofinformation to be stored in the allocation mobility associationinformation holding unit 203 of the MN 100. FIG. 3 is an illustration ofone example of an information storage table, in which an allocationmobility association information holding unit of an MN stores mobilityassociation information, according to the first embodiment of thepresent invention.

In the information storage table shown in FIG. 3, an ID (ID of an HA)for the identification of an HA in a home network to which the MN 100itself pertains, an address of an HA managing an HoA and information onan HoA of the MN 100 actually managed by this HA are stored in a stateassociated with each other. When the HoA of the MN 100 itself, theaddress of the HA which has allocated this HoA to the MN 100, and the IDfor the identification of this HA are held in a state associated witheach other, a plurality of HoAs are allocated to the MN 100 and, even ifseveral HoAs of the plurality of HoAs are managed by the same HA (thatis, in a case in which a plurality of HoAs are allocated from a homenetwork which is in a site multihome condition), the identificationbecomes feasible between the plurality of HoAs allocated from the homenetwork which is in a site multihome condition and an HoA allocated froma home network other than this home network.

As the method of allocating these mobility association information(information which may be changed due to movement of the MN 100), it isalso acceptable that they are set statically by a manager of the MN 100,and that they are acquired dynamically in a manner such that the MN 100interchanges messages through the transmission/reception unit 201 withrespect to an authentication server (not shown), an HA or the like.

Although FIG. 3 shows one example in which the information are managedby using the IDs of HAs and, if the IDs of the HAs are identical to eachother, even if the addresses of the HAs are different from each other,they are considered to be the same HA, it is also appropriate to make asimilar judgment on the basis of the addresses of the HAs without usingthe IDs of the HAs. However, in the case of the judgment based on theaddresses of the HAs, if the HA has a plurality of addresses, there is apossibility that the judgment is made as separate HAs. In such a case,it is preferable that the identification of the HA is made usinginformation such as ID other than the address so that the confirmationon the HA identify becomes feasible even in a case in which a single HAhas a plurality of addresses. Moreover, it is also acceptable to managethe information on the basis of only the ID of the HA without using theaddress of the HA.

In addition, referring to FIG. 4, a description will be givenhereinbelow of information (mobility association information) to behanded over from the connected network judging unit 204 to the notifiedHoA information holding unit 205 and the plural-HoA informationnotification message generating unit 206 in the MN 100. FIG. 4 is anillustration of one example of information a connected network judgingunit hands over to a notified HoA information holding unit and aplural-HoA information notification message generating unit in an MNaccording to the first embodiment of the present invention.

The connected network judging unit 204 associates information,indicative of whether or not it is currently in connection with the homenetwork which has allocated a plurality of HoAs, with the plurality ofHoAs held by the allocation mobility association information holdingunit 203. Moreover, in a case in which the MN 100 now allocates one HoAto an interface and a direct communication is possible through the useof this HoA, information indicative of the fact that it is in connectionwith the home network is added in a state associated with this HoA.

In the example shown in FIG. 4, the notified HoA information holdingunit 205 holds the information (home agent information) indicative ofthe fact that the PF1. HoA is managed by an HA identified the HA. ID1 orthe address thereof. Moreover, the notified HoA information holding unit205 holds the information indicative of the fact that the PF2. HoA andthe PF3. HoA are managed by an HA identified the HA. ID2 or the addressthereof. Still moreover, the notified HoA information holding unit 205holds the information indicative of the fact that the PF4. HoA ismanaged by an HA identified the HA. ID3 or the address thereof. Inaddition, since the MN 100 does not make a connection with any homenetwork at present but it is in connection with the foreign network, theinformation indicative of non-connection with the home network isappended to the home network connection information associated with allthe HoAs.

Referring to FIG. 5, a description will be given hereinbelow of HoAinformation included in a plural-HoA information notification messagegenerated by the plural-HoA information notification message generatingunit 206 in the MN 100. FIG. 5 is an illustration of one example of HoAinformation included in a plural-HoA information notification messagegenerated by a plural-HoA information notification message generatingunit in an MN according to the first embodiment of the presentinvention.

As shown in FIG. 5, the plural-HoA information notification messagecontains the ID of an HA, home network connection information, anaddress of an HA (HA. ID address) specified by the ID of the HA and eachfield for the insertion of an HoA managed by the HA.

When this plural-HoA information notification message is transmitted tothe CN 150, it is possible to notify, to the CN 150, the address of theHA managing the HoA and the home network connection informationindicative of whether or not the HoA is valid in the current MNconnection condition (that is, whether or not the MN is currently inconnection with the home network where this HoA is valid). That is, theinformation grasped and managed by the MN 100 as shown in FIG. 4 isnotified through the use of the plural-HoA information notificationmessage shown in FIG. 5, to the CN 150.

This plural-HoA information notification message carrying HoAinformation is not limited to a new message, but it is also appropriatethat, for example, similar information is included in a binding updatemessage based on the mobile IP and transmitted, and that the informationis included in a message according to a protocol handling site multihomeor host multihome and transmitted. Moreover, it is also appropriate togenerate a plural-HoA information notification message including onlyinformation on an HA managing an HoA but not including home networkconnection information, or to generate a plural-HoA informationnotification message including only the home network connectioninformation but not including information on an HA managing an HoA.

As described above, the MN 100 shown in FIG. 2 can hold plural-HoAinformation in a state associated with identification information on anHA which manages each HoA. Moreover, the MN 100 shown in FIG. 2 can holdthat, particularly, a plurality of HoAs (that is, a plurality of HoAsgenerated in a site multihome condition) are managed by the same HA.Still moreover, the MN 100 shown in FIG. 2 can further hold networkconnection information indicative of a home network with a valid HoA,with which it is currently in connection, in an associated state. Yetmoreover, the MN 100 shown in FIG. 2 can notify the above-mentionedplural-HoA information, HA identification information and networkconnection information to the CN 150 through the use of a plural-HoAinformation notification message.

Furthermore, referring to FIG. 6, a description will be givenhereinbelow of a configuration of a communication partner according tothe first embodiment of the present invention. FIG. 6 is a block diagramshowing one example of a configuration of a communication partneraccording to the first embodiment of the present invention. The CN 150shown in FIG. 6 is composed of a transmission/reception unit 601, an IPaddress acquiring unit 602, a plural-HoA information notificationmessage processing unit 603, a plural-HoA information holding unit 604,a transmission data generating unit (upper layer) 605, a transmissionpacket generating unit 606, a destination HoA selecting unit 607 and anHA inquiry executing unit 608. In FIG. 6, although the functions to berealized in the CN 150 are expressed by blocks, these functions arerealizable by hardware or software.

The transmission/reception unit 601 is connected through radiocommunication to a foreign network and has a function to make acommunication with an arbitrary node, which is in connection with adifferent network, through an arbitrary node in the foreign network andISP. This transmission/reception unit 601 includes one or morecommunication interfaces, and an IP address generated/acquired by the IPaddress acquiring unit 602 is allocated to each of the communicationinterfaces.

The IP address acquiring unit 602 fulfills a function to generate oracquire an IP address through the use of the address automatic setting(stateless address autoconfiguration), the DHCP, the manual setting orthe like for the purpose of obtaining a valid IP address in a networkconnected thereto. The IP address acquired by the IP address acquiringunit 602 is allocated to a communication interface held by thetransmission/reception unit 601.

The plural-HoA information notification message processing unit 603fulfills a function to conduct the processing on a plural-HoAinformation notification message received from the MN 100. Theplural-HoA information notification message processing unit 603 gives aninstruction so as to store the information, included in the plural-HoAinformation notification message received from the MN 100, in theplural-HoA information holding unit 604.

Upon receipt of an instruction from the plural-HoA informationnotification message processing unit 603, the plural-HoA informationholding unit 604 fulfills a function to store the information, includedin the plural-HoA information notification message received from the MN100. In the plural-HoA information holding unit 604, the informationsimilar in configuration to that shown in FIG. 4 is held for each MN100.

The transmission data generating unit (upper layer) 605 is an upperlayer for generating a data section to be included in a packet andsignifies an application and a transport layer such as TCP/UDP (UserDatagram Protocol) carrying the data.

The transmission packet generating unit 606 fulfills a function togenerate an IP packet including a data section generated by thetransmission data generating unit 605. At the generation of the IPpacket, the transmission packet generating unit 606 gives an instructionto the destination HoA selecting unit 607 for the selection of an HoA ofthe MN 100 to be set as a destination address of a transmission packet,and then sets the HoA selected by the destination HoA selecting unit 607as the destination address of the packet, and further hands over thispacket to the transmission/reception unit 601 and gives a transmissioninstruction thereto.

In addition, receipt of an instruction from the transmission packetgenerating unit 606, the destination HoA selecting unit 607 fulfills afunction to select an optimum HoA to be set as a destination address ofa packet generated by the transmission packet generating unit 606. Atthe selection of the optimum HoA, the destination HoA selecting unit 607refers to the information (for example, the information shown in FIG. 4)stored in the plural-HoA information holding unit 604. At this time, inthe case of giving priority to the optimized route, the destination HoAselecting unit 607 refers to the home network connection information andselects an HoA to which appended is the information indicative of theconnection with the home network, thereby enabling the packet to bedirectly transferred to that MN 100. On the other hand, for givingpriority to the HA condition, the destination HoA selecting unit 607gives an instruction to the HA inquiry executing unit 608 for making aninquiry at an HA managing each of the HoAs and then selects an HoA byreferring to the HA condition obtained as a result. When an HA indicatedby the HA information stored in the plural-HoA information holding unit604 is selected as an HA which is an object of inquiry, the execution ofthe inquiry processing is suppressible up to the degree still needed.

Moreover, upon receipt of an instruction from the destination HoAselecting unit 607, the HA inquiry executing unit 608 carries out afunction to transmit a message or the like to the HA related to theinstruction for making a request for information on the condition ofthis HA and to notify the information on the condition of the HA,acquired as a result, to the destination HoA selecting unit 607. In thisconnection, since the contents based on the information notified fromthe MN 100 are held in the plural-HoA information holding unit 604,instead of the address of the HA, the ID of the HA or the like issometimes used as the HA information. In this case, it is alsoacceptable that, for example, the HA inquiry executing unit 608generates a home agent anycast address from a prefix of an HoA of the MN100 and transmits an inquiry message with this address being set as adestination.

As the information indicative of the condition of the HA, for example,conceivable are information indicative of the current and futureconditions of the HA, information on the current processing load, amanagement domain of the HA, roaming thereof, and others. Theinformation indicative of the condition of the HA is not limited tothese pieces of information, provided that it is information usable forthe comparison/selection of the HA. Moreover, it is also possible toemploy a method in which a message for making a verification as towhether or not the HA is in operation is transmitted and, in the case ofno response, this HA is considered to be in a non-operating state and isremoved from the selection candidate. Still moreover, it is alsoacceptable that this message is used as information for the comparisonof a state of a QoS of a communication route between the CN 150 and theHA. Incidentally, the acquisition method and acquisition source for theinformation on the HA condition are not limited to these, but therequest can be made with respect to another HA existing in the homenetwork, and it can also be made to an intensively managing server.

In this connection, in a case in which the CN 150 does not select an HoAin consideration of the condition of the HA but an address is selectedon the basis of a policy on each HoA notified from the MN 100, the homenetwork connection information on the MN 100 can also be used as one ofthe conditions. Moreover, the home agent information on each HoA canalso be used as one of the conditions.

As described above, the CN 150 shown in FIG. 6 can acquire the mobilityassociation information on the MN 100 (for example, the informationillustrated in FIG. 4) and, at the selection of an HoA to be set as adestination address of a packet to be transmitted to the MN 100, it cangrasp whether or not the MN 100 is currently in connection with the homenetwork which is managing the HoA of the MN 100 itself (that is, whetheror not there is, of a plurality of HoAs, an HoA which allows a packet tobe sent directly to the MN 100 without passing through an HA.

In consequence, for example, in a case in which the HoA in the homenetwork with which the MN 100 is in connection is one of the pluralityof HoAs, the CN 150 selects this HoA, thereby enabling the directdelivery of a packet to the MN 100. This enables avoiding the transferroute passing through an HA which occurs in the case of the selection ofan HoA in the other non-connection home network, thereby achieving theroute optimization.

In addition, the CN 150 is also capable of selecting an HoA by taking astate of an HA into consideration. In this case, the CN 150 can searchan HoA, where the same HA information is set, to grasp that, of aplurality of HoAs, there exists an HoA managed by the same HA, whichallows specifying the HA which is an object of inquiry. This preventsfrequent inquiry operations at the same HA.

Furthermore, a brief description will be given hereinbelow of a concreteoperation according to the first embodiment of the present invention.For example, as shown in FIG. 1, let it be assumed that the MN 100 makesa communication with the CN 150 in a state where the MN 100 is inconnection with a foreign network. At this time, as mentioned above, theinformation shown in FIG. 4 is notified from the MN 100 to the CN 150through the use of a plural-HoA information notification message, andthe CN 150 can grasp the following two facts by the acquisition of thisinformation.

The first is that, on the basis of the home network connectioninformation, the CN 150 can see that the MN 100 is not currently inconnection with any home network but it is in connection with a foreignnetwork. In this case, even if the CN 150 selects and transmits everyHoA as a destination address, the packets reach the MN 100 through thecorresponding HA. Moreover, in a case in which there exists home networkconnection information indicative of in-connection with the homenetwork, the CN 150 selects a HoA corresponding to the home networkconnection information indicating that the MN 100 is in connectiontherewith and sets it as a destination address of a packet to betransmitted to the MN 100, thereby enabling the packet to run along anoptimized route and arrive at the MN 100.

The second is that, on the basis of the HA information, the CN 150 cangrasp that the PF2. HoA and the PF3. HoA which are HoAs of the MN 100are HoAs under management by the same HA2 lying in the home network 2.

Therefore, for example, for preventing a packet from being transmittedto an HA which is in a non-operating condition or for selecting the bestHA in a communication condition between the CN 150 and the HA, at theinquiry at each HA, when the CN 150 only once makes an inquiry at the HA2 lying in the home network 2, the CN 150 can easily seize the fact thatthe inquiry at the HA managing two HoAs of the PF2. HoA and the PF3. HoAreach completion. Moreover, the CN 150 selects an HoA according to theresult of the inquiry at the HA and sets it as a destination address ofa packet to be transmitted to the MN 100, which allows the packet to besent through the optimum HA to the MN 100.

As described above, according to the first embodiment of the presentinvention, even in a case in which, for example, for the reason that theMN 100 wants to prevent the CN 150 from knowing the position of amovement destination of the MN 100, the notification of a CoA is notmade through the use of a normal binding update message, since theplural-HoA information, the HA information for managing these HoAs andthe plural-HoA information notification message including the homenetwork connection information and others are transmitted from the MN100 to the CN 150, the CN 150 can seize that the MN 100 is in connectionwith the home network and an HoA in this home network is allocated to aninterface, and it can gasp that, when a packet is transmitted to thatHoA, the packet directly reaches the MN 100.

In addition, since the CN 150 can identify an HA managing a plurality ofHoAs held by the MN 100, the CN 150 becomes capable of grasping thesituation in which the plurality of HoAs are managed by the same HA and,even in the case of making an inquiry at the HA, it can accuratelyspecify the object HA so as to avoid the useless inquiry processing atthe HA, such as making an inquiry at the same HA several times.Likewise, also in the MN 100, it is possible to prevent the uselessprocessing at the inquiry at the HA.

Second Embodiment

Secondly, referring to FIG. 7, a description will be given hereinbelowof a configuration of a network according to a second embodiment of thepresent invention. FIG. 7 is an illustration of a first example of aconfiguration of a network according to a second embodiment of thepresent invention. The configuration of a communication system shown inFIG. 7 is only one example, and the present invention is not limited tothe configuration shown in FIG. 7.

In FIG. 7, there are shown three networks (home network 1 of MN 100,foreign network 1, foreign network 2), an MN 100 having two interfacesof an interface which is in connection with the home network 1 and aninterface which is in connection with the foreign network 1, and a CN150 which is in connection with the foreign network 2. Moreover, eachnetwork is connected through the internet 110, and an HA 1 which is ahome agent of the MN 100 exists in the home network 1.

The MN 100 shown in FIG. 7 has a plurality of interfaces so as to enablethe simultaneous connections with a plurality of different networks. AnHoA of the MN 100 is allocated to the interface connected to the homenetwork 1 and, in the following description, this address is referred toas HoA1. On the other hand, an address valid in the foreign network 1 isallocated to the interface connected to the foreign network 1 and thisaddress is handled as CoA. In the following description, this address isreferred to as a CoA1. The number of the interfaces held by the MN 100is not limited to two. Likewise, the numbers of home networks to beallocated to the MN 100, foreign networks and home agents are notlimited to the configuration shown in FIG. 7. One or a plurality isacceptable.

FIG. 7 shows a case in which one of the networks with which the MN 100is in connection is a home network for the MN 100 and the other is aforeign network for the MN 100. Whether the network with which the MN100 is in connection is a home network or a foreign network depends uponthe judgment as to whether this MN 100 recognizes that network as a homenetwork or a foreign network. For example, conceivable are a method ofmaking a judgment on the basis of which of the networks is theconnection-accepting network to the MN 100, a method of making ajudgment which of the networks the MN 100 itself configures as theconnection-accepting network and a method of using a combination of boththe judgments. In the case of the former judgment method, it isconsidered that the recognition on the network by the MN 100 dependsupon the information on the home network allocated dynamically orstatically, while in the case of the latter judgment method, it isconsidered that the network recognition depends on a configuration takenby the MN 100 itself. In FIG. 7, the home network and the foreignnetwork have a configuration the MN 100 recognizes.

The second embodiment of the present invention will be describedhereinbelow in consideration of a case in which, in the networkconfiguration shown in FIG. 7, in a state where the MN 100 uses twointerfaces to establish the connections with the home network 1 and theforeign network 1 at the same time, the MN 100 makes a communicationwith the CN 150 through the use of both the interfaces.

First, a description will be given of a configuration of the MN 100according to the second embodiment of the present invention. FIG. 8 is ablock diagram showing one example of a configuration of the MN 100according to the second embodiment of the present invention. The MN 100shown in FIG. 8 is composed of a transmission/reception unit 801, an IPaddress acquiring unit 802, an allocation mobility associationinformation holding unit 803, a connected network judging unit 804, anotified HoA information holding unit 805 and a binding informationnotification message generating unit 806. In FIG. 8, although functionsrealized in the MN 100 are shown by blocks, these functions arerealizable by hardware or software. The transmission/reception unit 801,the IP address acquiring unit 802 and the allocation mobilityassociation information holding unit 803 are the same as thetransmission/reception unit 201, the IP address acquiring unit 202 andthe allocation mobility association information holding unit 203, andthe description thereof will be omitted.

The connected network judging unit 804 fulfills a function to make ajudgment as to which of the networks it is in connection. The connectednetwork judging unit 804 acquires a prefix of its own home network fromthe allocation mobility association information holding unit 803 andmakes a comparison between it and a prefix in the network with which ithas established a connection. If both agree with each other, a judgmentis made that it is in connection with the home network. If they do notagree with each other, a judgment is made that it is in connection withthe foreign network. The connected network judging unit 804 hands over aresult of the judgment (home network connection information indicativeof whether or not the connection-accepting network is the home network)to the IP address acquiring unit 802. The connected network judgingmethod is not limited to the above-mentioned method, but it is alsoacceptable to employ an arbitrary method whereby a variation of theconnected network is detectable.

In addition, in a case in which the connected network judging unit 804makes a judgment that the network connected to the interface of the MN100 is the home network, the connected network judging unit 804 handsover the information (in-connection information) indicative of the factthat the connection-accepting network is the home network to thenotified HoA information holding unit 805 and gives an instructionthereto for holding this information and further hands it over to thebinding information notification message generating unit 806 and givesan instruction thereto for generating a binding information notificationmessage which is for notifying the information to an HA and/or the CN150.

On the other hand, if the connected network judging unit 804 makes ajudgment that the network connected to the interface of the MN 100 isthe foreign network, the connected network judging unit 804 hands overan address (CoA) allocated to the interface connected to this foreignnetwork and an HoA for the association of this CoA to the notified HoAinformation holding unit 805 and gives an instruction thereto forholding this information and further hands it over to the bindinginformation notification message generating unit 806 and gives aninstruction thereto for generating a binding information notificationmessage which is for notifying the information (CoA associatedinformation) to the HA and/or the CN 150.

It is also appropriate that, in a case in which the connected networkjudging unit 804 makes a judgment that the network connected to theinterface of the MN 100 is the foreign network, the connected networkjudging unit 804 hands over the information (non-connectioninformation), indicative of the fact that the connection-acceptingnetwork is not the home network, to the notified HoA information holdingunit 805 and gives an instruction thereto for holding this information,and further hands it over to the binding information notificationmessage generating unit 806 and gives an instruction thereto forgenerating a binding information notification message which is fornotifying the information to an HA and/or the CN 150.

In this case, it is also acceptable that the non-connection informationand the CoA association information are handled as information relatedto the same interface and pluralities of information are notifiedsimultaneously or separately. Moreover, it is also acceptable that onlythe information to be notified is selected and notified. Still moreover,it is also possible that the home network connection information and theCoA association information, related to the respective interfaces, arenotified simultaneously as information on a plurality of interfaces ofthe MN 100, or that they are notified separately. Likewise, with respectto these pieces of information, only the information to be notified canalso be selected and notified.

In the following description, the information indicative of the factthat the MN 100 is in connection with the home network will be referredto as in-connection information, the information indicative of the factthat the MN 100 is not in connection with the home network will bereferred to as non-connection information and, when these twoinformation are put together, the information indicative of whether ornot the MN 100 is in connection with the home network will be referredto as home network connection information. Moreover, the bindinginformation including the in-connection information and thenon-connection information will sometimes be referred to as home networkconnection information.

The binding information notification message generating unit 806fulfills a function to generate a binding information notificationmessage including the home network connection information notified fromthe connected network judging unit 804, and hand over the bindinginformation notification message to the transmission/reception unit 801and give an instruction thereto for the transmission thereof.

As the binding information notification message, a binding updatemessage according to the mobile IP is usable, and a message based on adifferent protocol or a newly generated message is also available. Ifthe information shown in FIG. 9A or 9B and mentioned later can benotified to a destination, every format is acceptable. Through the useof the binding information notification message, the MN 100 notifies, toa destination, the information for specifying an HoA which is an objectof registration and the information indicating that this HoA is anaddress allocated to the interface connected to the home network.Moreover, it is also appropriate that the MN 100 notifies, to thedestination, the information (information including non-connectioninformation) shown in FIG. 9C or 9D and mentioned later. Also in thiscase, a message with every format is available.

With respect to the transmission of the home network connectioninformation, it is preferable to make the notification of thein-connection information when the MN 100 establishes a connection withits own home network or when it is in connection therewith. On the otherhand, it is preferable to notify the non-connection information when theMN 100 itself is not connected to the home network. Moreover, it is alsoacceptable to make the transmission at the same timing as the bindingupdate based on the mobile IP. It is also appropriate that the homenetwork connection information is not always transmitted at theconnection with the home network, the in-connection therewith and thenon-connection therewith but the transmission is arbitrarily madeaccording to a decision by a user or operator. Still moreover, thedestination of the binding information notification message is notlimited to the nodes (HA1 and/or CN 150) constituting the network shownin FIG. 7, but all nodes are acceptable, provided that they can utilizethe home network connection information and the CoA associationinformation on the MN 100. For example, the transmission can also bemade to a proxy node serving as a proxy for the HA or CN 150 and made toa management node having a function to manage the information on the MN100.

In addition, in a case in which the CoA association information on adifferent address allocated to the same interface or a differentinterface and the home network connection information are held in thenotified HoA information holding unit 805, or when a judgment is madethat the notification of these pieces of information is necessary, it isalso appropriate that these pieces of information are also included inthe binding information notification message generated to notify theabove-mentioned home network connection information and CoA associationinformation before being transmitted. For example, in the case of the MN100 in the configuration shown in FIG. 7, the home network connectioninformation on the interface connected to the home network 1 and thebinding information on the interface connected to the foreign network 1can be transmitted through the use of separate binding informationnotification messages, and they can also be transmitted in a stateincluded in a single binding information notification message.

Still additionally, in a case in which the MN 100 is in connection withthe foreign network 1 and the foreign network 3 as shown in FIG. 10, theCoA association information on the interface connected to the foreignnetwork 1 and/or the foreign network 3 and the non-connectioninformation, which is home network connection information, can betransmitted through the use of separate binding information notificationmessages, and they can also be transmitted in a state included in asingle binding information notification message.

Yet additionally, the notified HoA information holding unit 805 exhibitsa function to hold the binding information handed over from theconnected network judging unit 804 and notified to the HA or CN 150. Inthe notified HoA information holding unit 805, as well as the CoAassociation information indicative of the association between an HoA anda CoA, transmitted through the use of a binding update message based onthe normal mobile IP, the in-connection information indicative of theconnection with the home network and the non-connection informationindicative of the non-connection with the home network are also held asthe information transmitted from the MN 100 to its own HA or the CN 150.It is also acceptable that the notified HoA information holding unit 805is realized as a binding update list specified in the mobile IP, or thatit is realized with a different data holding unit.

Furthermore, referring to FIGS. 9A, 9B, 9C and 9D, a description will begiven hereinbelow of the information (home network connectioninformation) the connected network judging unit 804 hands over to thenotified HoA information holding unit 805 and the binding informationnotification message generating unit 806 in the MN 100. FIGS. 9A and 9Bare illustrations of first and second examples of the in-connectioninformation the connected network judging unit 804 hands over to thenotified HoA information holding unit 805 and the binding informationnotification message generating unit 806 in the MN 100 according to thesecond embodiment of the present invention.

As shown in FIG. 9A, the connected network judging unit 804 appends, tothe HoA1 allocated to the interface connected to the home network 1, theinformation indicative of the fact that it is currently in connectionwith the home network 1 which has allocated this HoA1. As shown in FIG.9B, it is also possible to append simultaneously the information on theaddress (CoA1), allocated to a different interface, to as a CoAassociated with the HoA1.

Moreover, FIGS. 9C and 9D are illustrations of first and second examplesof the non-connection information the connected network judging unit 804hands over to the notified HoA information holding unit 805 and thebinding information notification message generating unit 806 in the MN100 according to the second embodiment of the present invention. Theinformation shown in FIGS. 9C and 9D indicates a state in which, asshown in FIG. 10, the MN 100 is in connection with the foreign network 1and the foreign network 3 and the CoA1 and the CoA3 are allocated to theinterfaces connected to the foreign network 1 and the foreign network 3,respectively.

As shown in FIG. 10, in a case in which the MN 100 is in connection withthe foreign network 1 and the foreign network 3 and the CoA1 isallocated from the foreign network 1 while the CoA3 is allocated fromthe foreign network 3, as shown in FIG. 9C, the connected networkjudging unit 804 appends, to its own HoA1, the information indicative ofthe fact that it is not currently in connection with the home network 1which has allocated this HoA1. It is also acceptable that, as shown inFIG. 9D, the information on the addresses (CoA1 and CoA3) allocated tothe respective interfaces is simultaneously appended thereto as CoAsassociated with the HoA1.

The MN 100 can transmit a binding information notification message,generated by the binding information notification message generatingunit 806, to the HA and/or the CN 150 so as to notify, to the HA and/orthe CN 150, the information which is indicative of the fact that theHoA1 is an address allocated to the interface which is in connectionwith the home network and which is independent from the information onan address allocated to a different interface. The MN 100 can notifythat the MN 100 is in connection with the foreign network but not inconnection with the home network. That is, as shown in FIGS. 9A to 9D,the information grasped and managed by the MN 100 is notified to the HAand/or the CN 150 through the use of a binding information notificationmessage.

For the binding information notification message carrying the homenetwork connection information, for example, as shown in FIG. 11, a newflag (N flag) is added to a reserved field as an extension of aconventional binding update message (see the Non-Patent Document 2)based on the mobile IP. In this case, when this flag is set, it canindicate a binding update message according to the second embodiment ofthe present invention and indicate the fact that the HoA included in themessage is an address allocated to the interface connected to the homenetwork. Moreover, for a message using a mobility header specified inthe mobile IP, it is also appropriate that a new mobility message towhich a new mobility header type is allocated is produced and used ashome network connection information.

Moreover, with respect to the information to be notified, the bindinginformation notification message according to the present invention isindicated by various types of field values, flags and combinationsthereof to be appended to a binding update message to be transmitted forthe registration or deletion of the CoA association informationindicative of the association between an HoA and a CoA, specified in theconventional mobile IP, and necessary information is added thereto.

Still moreover, it is also appropriate that, in the binding updatemessage for notifying the CoA association information, the HoA on thein-connection information is specified in a section for specifying theHoA and CoA to be registered, thereby notifying the fact of theconnection with the home network to the communication partner. Yetmoreover, it is also acceptable that, in the binding update message forthe deletion of the CoA association information, the HoA on thenon-connection information is specified in a section for specifying theHoA and CoA to be deleted, thereby notifying the fact of no connectionwith the home network to the communication partner. According to themobile IP, although the CoA association information is notified to theHA or the CN 150 through the use of a home address option carried by adestination option header based on the IPv6, it is also possible toextend this option so as to indicate the home network connectioninformation, and it is also possible that the home network connectioninformation is carried by use of a different option type.

In addition, as shown in FIG. 12, it is also acceptable that a newoption is produced as one of mobility options to be appended to abinding update message and necessary information is put therein andtransmitted. Still additionally, as shown in FIG. 13, it is alsoappropriate that a new option different from the mobility options isproduced and necessary information is put therein and transmitted.

Yet additionally, in a case in which, for enabling the HA and/or the CN150 to distinguish among a plurality of CoA association information, theMN 100 appends an ID to each of the information or to a message carryingthis information, it is also appropriate that a home CoA flag is set inan option including this ID.

The binding information notification message is not limited to theextension of a binding update message based on the mobile IP asmentioned above. For example, it is also acceptable that these pieces ofinformation are included in a message based on a protocol handling themultihome and transmitted, and that a new message for carrying thesepieces of information is produced and put to use. Moreover, it is alsoacceptable that these pieces of information are put in the plural-HoAinformation notification message containing the information on the HAmanaging the HoA, mentioned above in the first embodiment of the presentinvention.

Furthermore, even in a case in which the MN 100 which is made to notifya plurality of CoA association information to a communication partnerthrough the use of separate binding update messages appends a unique IDto each message so that the communication partner can distinguishbetween the respective binding update messages, the MN 100 can appendsuch a unique ID to the binding update message including the homenetwork connection information. Moreover, likewise, even in a case inwhich IDs are appended to the respective binding information and theyare transmitted through the use of separate binding update messages andin a case in which a plurality of binding information are transmittedwith the same binding update message, such an ID can be appended to thebinding information including the home network connection information.Thus, the communication partner can achieve the registration,replacement and deletion of the home network connection information,included in the received message, according to the appended ID.

Still furthermore, in a case in which the MN 100 notifies a policy onthe destination address selection to the CN 150, it is also appropriateto append similar policies to not only the CoA association informationbut also in-connection information and then transmit them.

Yet furthermore, it is also appropriate to transmit a normal bindingupdate message for the deletion of the CoA association information or abinding update message for the detection of the CoA associationinformation to which appended is the information indicative of theinclusion of the home network connection information and to give aninstruction to the communication partner, which has received thismessage, for correcting or replacing the held entry which is of anobject of deletion and holding the new home network connectioninformation.

When the MN 100 itself transmits a packet, it is also possible to carryout the source address selection using the home network informationnotified to the HA and/or the CN 150. Moreover, also in the case ofmanaging a plurality of addresses held by the MN 100 itself and mappingthese addresses into the IDs (addresses) to be notified to an upperlayer, it is also possible to utilize the home network connectioninformation for the address selection for this function. Even if themapping function exists, it can function as a destination addressselecting unit independent of this function.

Furthermore, a description will be given hereinbelow of an operation ofthe MN 100 in consideration of the states of the MN 100 before and aftermovement.

(Case of the CoA Association Information Before the Movement and theHome Network Connection Information after the Movement)

In a case in which, with respect to an address acquired before theinterface, which has established a connection with the home network,establishes the connection therewith, an entry indicative of theregistration of the binding information on the association between thisaddress and an HoA in the HA and/or the CN is held in the notified HoAinformation holding unit 805, the connected network judging unit 804gives an instruction to the binding information notification messagegenerating unit 806 for making a request for replacing the old addressassociated with the HoA with the home network connection information.

In this case, with respect to the binding information notificationmessage to be generated by the binding information notification messagegenerating unit 806, for example, in the case of a binding updatemessage based on the mobile IP, as shown in FIG. 14, an HoA which ishome network connection information to be notified can be put in a homeaddress option (or a new option) specified in the mobile IP while, asthe information for specifying the CoA association information which isan object of replacement of the home network connection information, theCoA can be put in an alternate CoA (alternate Care-of Address) option tobe employed for a binding update message according to the normal mobileIP.

In addition, as shown in FIG. 15, it is also acceptable that the addressspecified as the source address of the binding information notificationmessage is set as an HoA to be notified as the in-connectioninformation. Still additionally, as shown in FIG. 16, it is alsoacceptable that, instead of the alternate CoA option, the addressspecified as the source address of the binding information notificationmessage is set as a CoA included in the CoA association informationwhich is an object of replacement.

The binding information notification message can include, for example:

-   -   information for specifying an HoA which is an object of        registration;    -   home network connection information indicating that this HoA is        an HoA allocated to an interface which is in connection with a        home network;    -   and    -   information for specifying CoA association information to be        replaced with this HoA.

All formats are acceptable, provided that information can be notified toa destination. Moreover, in the case of no CoA association informationto be replaced, there is no need to include this information. Stillmoreover, it is also appropriate that the type of a message to benotified is made to identify the fact that the HoA which is an object ofregistration is an HoA allocated to the interface connected to the homenetwork.

(Case of Home Network Connection Information Before and after Movement)

In a case in which an address acquired before the interface, which hasestablished a connection with the home network, establishes theconnection therewith is held as home network connection information inthe notified HoA information holding unit 805, the connected networkjudging unit 804 notifies, as an HoA connected to the home network, theold address information notified to the HA and/or the CN 150 and theinformation for specifying the address to be replaced with this homenetwork connection information.

In this case, the binding information notification message to begenerated by the binding information notification message generatingunit 806 can include, for example:

-   -   information for specifying an HoA which is an object of        registration;    -   home network connection information indicating that this HoA is        an HoA allocated to an interface which is in connection with a        home network; and    -   information for specifying the Home Network connection        information to be replaced with this HoA.

All formats are acceptable, provided that information can be notified toa destination. Moreover, in the case of no CoA association informationto be replaced, there is no need to include this information. Stillmoreover, it is also appropriate that the type of a message to benotified is made to identify the fact that the HoA which is an object ofregistration is an HoA allocated to the interface connected to the homenetwork.

(Case of Home Network Connection Information Before Movement and CoAAssociation Information after Movement)

In a case in which an address acquired before the interface, which hasestablished a connection with the foreign network, establishes theconnection therewith is held as home network connection information inthe notified HoA information holding unit 805, the connected networkjudging unit 804 gives an instruction to the binding informationnotification message generating unit 806 so as to generate a bindinginformation notification message for making a request for replacing theold address information notified as an HoA connected to the home networkto its own HA and/or the CN 150 with the CoA association information onthe association of the CoA with the HoA.

In this case, the binding information notification message to begenerated by the binding information notification message generatingunit 806 can include, for example:

-   -   information for specifying an CoA which is an object of        registration;    -   information for specifying an HoA with which a CoA is        associated; and    -   information for specifying the home network connection        information to be replaced with binding information including        this CoA.

All formats are acceptable, provided that information can be notified toa destination. Moreover, in the case of no home network connectioninformation to be replaced, there is no need to include thisinformation. Still moreover, it is also appropriate that the type of amessage to be notified is made to identify the fact that the CoA whichis an object of registration is a CoA with which the home networkconnection information is replaced.

As described above, the MN 100 shown in FIG. 8 is capable of notifying,to communication nodes such as its own HA and/or the CN 15, through theuse of a binding information notification message, the fact that theaddress allocated to the interface is an HoA allocated from the homenetwork under the connection. Since the information to be registeredthrough this notification can exist independently of the normal CoAassociation information (association between an HoA and a CoA), the MN100 can notify, to its own HA and/or the CN 150, the fact that it ispossible to receive both a packet addressed to the HoA and anencapsulated packet addressed to the CoA.

In addition, the MN 100 can notify the fact that it is in connectionwith the foreign network and is not in connection with the home network.In this case, the MN 100 can notify, to the HA1 and/or the CN 150, thefact that all the packets addressed to this HoA pass through the HA1 andreach the MN 100. Thus, even if the CoA association information on theMN 100 is not registered, the HA1 and/or the CN 150 can grasp that theMN 100 is not in connection with the home network.

Still additionally, it is also appropriate that, in addition to thein-connection/non-connection information, as one of the home networkconnection information, the MN 100 notifies the information (HAuse-inhibition information) for making a request for inhibiting thecommunication through the HA, for example, in a case in which sometrouble has occurred in the HA managing the HoA or when thecommunication through the HA is not preferable for other arbitraryreasons. Upon receipt of this notification, it is desirable that anodemakes a transmission to the CoA through the use of the routeoptimization based on the mobile IP without using the HoA as adestination address.

Also in a case in which the MN 100 has a plurality of HoAs (for example,HoA1 and HoA2) and the HoA1 is used as an address associated with theHoA2, it is also acceptable that this address is notified tocommunication nodes such as the HA and/or the CN 150 as an HoAcorresponding to the home network connection information (in-connectioninformation, non-connection information) or the HA use-inhibitioninformation. In this case, if a CoA section registered is an HoA servingas the in-connection information, the HA and/or the CN 150 can grasp thefact that the CoA of the MN 100 registered is an HoA on the interfaceconnected to the home network and, when this CoA is transmitted as adestination, they can grasp the fact that a packet can be directlydelivered to the MN 100. Moreover, when the CoA section is an HoAserving as the non-connection information, the HA and/or the CN 150 cangrasp the fact that the CoA of the MN 100 registered is an HoA which isnot connected to the home network and further, when this CoA istransmitted as a destination, they can seize the fact that a packet canbe delivered through the HA to the MN 100.

Furthermore, in a case in which the MN 100 uses a given HoA in a stateassociated with a CoA of a different HoA, when the informationexplicitly indicating that the CoA is the HoA is appended in a bindinginformation notification message (binding update message), the HA and/orthe CN 150 can recognize that a packet transmitted using this CoAassociation information is sent to the HoA of the MN 100. Stillfurthermore, in a case in which the home network connection informationaccording to the present invention is appended to the HoA serving as theCoA, the HA and/or the CN 150 can grasp that a packet transmitted tothis CoA is directly sent to the MN 100 or that the packet is sentthrough the HA thereto. If the home network connection informationaccording to the present invention is not appended thereto, the HAand/or the CN 150 cannot make a judgment as to whether the packettransmitted to this CoA is directly sent or sent through the HA managingthe HoA serving as the CoA.

For example, although the HA can recognize that an encapsulated packetaddressed to the MN 100 and generated using the CoA associationinformation to which the information indicative of the CoA being the HoAis added is transmitted to the HoA of the MN 100, the HA cannot make ajudgment as to whether the packet is directly sent to the MN 110 or sentthereto through a different HA. On the other hand, for example, in acase in which the non-connection information is added as the homenetwork connection information according to the present invention, theHA can recognize the fact that the encapsulated packet again passesthrough at least one of different Has. Meanwhile, although, by using theCoA association information to which the information indicative of theCoA being the HoA is appended, the CN 150 can recognize that the packetdirected to the MN 100 and generated by use of a routing header istransmitted to the HoA of the MN 100 as well as the above-mentioned caseof the HA, the CN 150 cannot judge whether the packet is directly sentto the MN 100 or sent thereto through the HA managing this HoA. In acase in which the in-connection information is added as the home networkconnection information according to the present invention, the CN 150can recognize that the packet transmitted directly arrives at the MN 100connected to the home network. Thus, the HA and/or the CN 150 can carryout the address selection on the basis of these recognition. Moreover,when the non-connection information is appended to the HoA serving asthe CoA, the HA and/or the CN 150 can recognize that there is apossibility that a CoA associated with the HoA indicated as that CoAexists, which creates a ground for making a request for further CoAassociation information to the MN 100.

Furthermore, referring to FIG. 17, a description will be givenhereinbelow of a configuration of an HA according to the secondembodiment of the present invention. FIG. 17 is a block diagram showingone example of a configuration of an HA according to the secondembodiment of the present invention. The HA shown in FIG. 17 includes atransmission/reception unit 1701, an HoA addressed packet proxyreception unit 1702, a binding information notification messageprocessing unit 1703, a binding information holding unit 1704, atransfer packet generating unit 1705, and a destination addressselecting unit 1706. In FIG. 17, although functions realized in the HAare shown by blocks, these functions are realizable by hardware orsoftware.

The transmission/reception unit 1701 is connected to its own network(home network) and fulfills a function to make a communication with anarbitrary node, connected to a different network, through an arbitrarynode in the home network and an ISP.

The HoA addressed packet proxy reception unit 1702 has a function toproxy-receive a packet addressed to the HoA of the MN 100. Upon receiptof the packet directed at the HoA, the HoA addressed packet proxyreception unit 1702 hands over this packet to the transfer packetgenerating unit 1705 and gives an instruction thereto for transferringit to the MN.

The binding information notification message processing unit 1703 has afunction to conduct the processing on a binding information notificationmessage received from the MN 100. The binding information notificationmessage processing unit 1703 gives an instruction to the bindinginformation holding unit 1704 to hold the home network connectioninformation, for example, included in a binding update message as shownin FIG. 11, in the binding information holding unit 1704.

For example, in a case in which the information on the old addressacquired before the MN 100 establishes a connection with the homenetwork is included as the information to be replaced with the notifiedhome network connection information or the CoA association informationin the binding information notification message, the binding informationnotification message processing unit 1703 gives an instruction to thebinding information holding unit 1704 so as to replace the informationon the old address with the notified home network connection informationor the CoA association information.

Moreover, upon receipt of the instruction from the binding informationnotification message processing unit 1703, the binding informationholding unit 1704 fulfills a function to store the home networkconnection information included in the binding information notificationmessage received from the MN 100 or the CoA association information. Thebinding information holding unit 1704 is made to hold the informationsimilar in contents to the above-mentioned information shown in FIGS. 9Ato 9D for each MN 100. The binding information holding unit 1704 can berealized as a binding cache specified in the mobile IP, or it can alsobe realized with a different data holding unit.

Still moreover, in a case in which, as shown in FIG. 9B, there arecontained not only the home network connection information but also theCoA association information on the address allocated to a differentinterface, the binding information holding unit 1704 holds both theinformation of the home network connection information and the CoAassociation information. The method of holding the informationindicative of the HoA connected to the home network is not limited tothe method of producing a different entry as mentioned above, it is alsoacceptable that, for example, information (flag or the like) indicativeof the connection with the home network is appended into the entry ofthe CoA association information indicative of the normal associationbetween an HoA and a CoA so as to indicate that not only the HoAincluded in this entry is associated with the CoA allocated to theinterface connected to the foreign network but also the HoA is anaddress allocated to the interface connected to the home network.

In addition, it is also appropriate that, when an entry which does notinclude the CoA association information is produced and only the homenetwork connection information is added thereto, the HoA included inthis entry indicates an address allocate to the interface to the homenetwork although there is no CoA associated therewith. Stilladditionally, it is also appropriate that an entry holding only the homenetwork connection information and an entry holding the CoA associationinformation are separately held and the fact of these plurality ofentries pertaining to a specific MN 100 is grasped by unique informationsuch as an HoA or ID.

The transfer packet generating unit 1705 fulfills a function totransfer, to the MN 100, a packet handed over from the HoA addressedpacket proxy reception unit 1702 and addressed to the HoA of the MN 100.At the generation of the transfer packet, the transfer packet generatingunit 1705 gives an instruction to the destination address selecting unit1706 for selecting an address designated as a destination address of thetransfer packet and, if the address selected by the destination addressselecting unit 1706 is the HoA, hands over the proxy-received packetdirectly to the transmission/reception unit 1701 while, if it is theCoA, generating a packet encapsulated into an outer header and directedto this address and handing over this packet to thetransmission/reception unit 1701 and giving an instruction for thetransmission thereof.

Moreover, the destination address selecting unit 1706 has a function toreceive an instruction from the transfer packet generating unit 1705 andselect an optimum address to be set as a destination of the transferpacket. For the selection of the optimum address, the destinationaddress selecting unit 1706 refers to the information (for example, theinformation shown in FIG. 9B) stored in the binding information holdingunit 1704. At this time, if it includes the CoA association informationindicative of the normal association between the HoA and the CoA and thehome network connection information, the destination address selectingunit 1706 selects one of the information. In a case in which thedestination address selecting unit 1706 selects the in-connectioninformation as the home network connection information, the packet whosedestination address is set to the HoA1 is transmitted without carryingout the route optimization, which eliminates the implementation of extraprocessing such as encapsulation and enables the direct transmission ofthe packet to the MN 100. In the case of the selection of the bindinginformation between the HoA and CoA, the destination address is set tothe CoA1 and the transmission is made in a state encapsulated, therebyallowing the continuous communication.

In this connection, in a case in which the destination address selectingunit 1706 utilizes a function to manage a plurality of addressesnotified from the MN 100 and map these addresses into an ID (address)notified to the upper layer, the destination address selecting unit 1706can also play a role as an address selecting unit for this function.Even if a mapping function exists, it can also function as a destinationaddress selecting unit independently of that function.

Although not shown, it is also appropriate that, after the reception ofa binding information notification message including the home networkconnection information such as a home CoA flag from the MN 100, an HA(for example, the HA shown in FIG. 17) according to the presentinvention puts, in a response message thereto, the informationindicative of a result of the reception of the home network connectioninformation notification from the MN 100 before the transmissionthereof. In this case, there is a need for the MN 100 which receivesthis response message to have a function for interpreting thisinformation.

In addition, although not shown, it is also appropriate that an HA (forexample, the HA shown in FIG. 17) according to the present inventionputs a flag in a router advertisement message, it transmits, so as toindicate that it handles a function on the home network connectioninformation. In this case, there is a need for the MN 100 which receivesthis message to have a function for interpreting this flag. When theflag is set in the message, the MN 100 makes a judgment that it ispossible to notify the information on the home network connectioninformation to the HA in the home network. On the other hand, if theflag is not set in the message, the MN 100 makes a judgment that it isimpossible to notify the information on the home network connectioninformation to the HA in the home network.

As the means for representing the information indicative of the factthat the HA handles the function on the home network connectioninformation, it is also possible to use a dynamic message such as DHCPv6or employ a static setting means by an operator or user. Moreover, it isalso possible that a new flag is provided in a request message of DHAADspecified in the mobile IPv6 and the request message in which thismessage is set indicates a request for a list of the HAs handling thefunction related to the home network connection information. Stillmoreover, it is also possible that a new flag is also provided in areply message thereto so as to indicate a message including a list ofthe HAs handling the function related to the home network connectioninformation.

It is also acceptable that a new flag is provided in a home agentinformation option specified in the mobile IPv6 so that the setting ofthis flag signifies that the HA indicated by this option is an HAhandling the function related to the home network connectioninformation.

As described above, the HA shown in FIG. 17 is capable of acquiring thebinding information on the MN 100 and of holding the information (homenetwork connection information) on the connection condition of the MN100 with respect to the home network. Simultaneously with the holding ofthe home network connection information, it is also possible to hold theCoA association information in which an address allocated to a differentinterface connected to a different network is associated as a CoA.

In consequence, for the selection of the destination address at thetransfer of a packet to the MN 100, the HA shown in FIG. 17 canpreferentially select the transmission to the interface connected to thehome network of the MN 100. For example, in a case in which adisconnection occurs between the MN 100 using the HoA as the destinationaddress and the CN 150, the HA can select the CoA associated with thisHoA and proxy-receive a packet addressed to the HoA to encapsulate apacket, which takes this HoA as the destination address, and transmit itto the CoA associated with this HoA, thereby achieving the promptrecovery of the communication. This also applies to a converse case. Inthis case, for example, when a disconnection occurs between the MN 100using the CoA as the destination address and the CN 150, by referring tothe home network connection information, it is possible to select, fromthe binding information related to this HoA, an address for thetransmission to the interface connected to the home network. Thus,although, in a normal condition, there is a need to wait for a bindingupdate message transmitted from the MN 100 at the occurrence of thedisconnection of communication, the employment of the method describedin the second embodiment of the present invention enables simultaneouslyholding the information on the HoA connected to the home network and theinformation on the HoA associated with the CoA, which provides anadvantage in that the destination can be switched in a moment so as tominimize the packet loss.

In addition, even in a case in which the HA uses the HoA as adestination address of a packet to be transmitted to the MN 100, as wellas the case of the route optimization using the CoA, the HA can graspthe fact of the direct arrival of the packet at the MN 100. Inparticular, in a case in which the HA holds a plurality of CoAassociation information on the MN 100 and receives the notification forthe registration of the in-connection information from the MN 100, sincenewly produced entries or entries other than a replaced entry are leftas they stand, the HA can grasp the CoA association information on theMN 100 and the fact of the connection of the MN 100 with the homenetwork. Still additionally, with respect to the selection of adestination address of a transfer packet addressed to the MN 100, the HAcan hold a policy for preferentially selecting the transfer to theinterface connected to the home network of the MN 100. When the homenetwork connection information according to the present invention isadded to an entry of the binding information, the HA can carry out thedestination address selection according to the aforesaid policy.

Furthermore, referring to FIG. 18, a description will be givenhereinbelow of a configuration of the CN 150 according to the secondembodiment of the present invention. FIG. 18 is a block diagram showingone example of a configuration of a CN according to the secondembodiment of the present invention. The CN 150 shown in FIG. 18 iscomposed of a transmission/reception unit 1801, a binding informationnotification message processing unit 1802, a binding information holdingunit 1803, a received packet processing unit 1804, a transmission packetgenerating unit 1805 and a destination address selecting unit 1806. InFIG. 18, although functions realized in the CN 150 are shown by blocks,these functions are realizable by hardware or software. Thetransmission/reception unit 1801, the binding information notificationmessage processing unit 1802 and the binding information holding unit1803 are the same as the transmission/reception unit 1701, the bindinginformation notification message processing unit 1703 and the bindinginformation holding unit 1704 in the HA shown in FIG. 17, respectively,and the description thereof will be omitted.

The transmission packet generating unit 1805 is for generating a packetto be transmitted to a communication partner and further for giving aninstruction to the destination address selecting unit 1806 for theaddress selection taking into consideration the binding information heldby the binding information holding unit 1803, thereby carrying out thepacket processing (packet conversion processing or the like) on thebasis of the address selected by the destination address selecting unit1806. If the selected address is a CoA, since the packet addressed tothe MN 100 is transmitted through the use of the route optimizationbased on the mobile IP, the packet conversion is made according to themethod specified in the mobile IP and the converted packet is handedover to the transmission/reception unit 1801. On the other hand, whenthe selected address is an HoA, the packet addressed to the HoA isdirectly handed over to the transmission/reception unit 1801 withoutcarrying out the packet conversion.

The received packet processing unit 1804 conducts the processing on apacket received from the MN 100. In a case in which the received packetis a packet converted for the route optimization based on the mobile IP,for restoring the converted packet to the original packet, aconfirmation is made as to whether or not the information on the HoA isheld in the binding information holding unit 1803. When the CoAassociation information related to this HoA is held therein, arecognition is made that the packet received from the MN 100 has beentransmitted through the use of the route optimization based on themobile IP.

Moreover, even in a case in which the received packet is a normalpacket, the received packet processing unit 1804 can also make aconfirmation as to whether or not the information on the address set asthe source address of this packet is held in the binding informationholding unit 1803. If the confirmation result shows that the homenetwork connection information related to this address is held in thebinding information holding unit 1803, the received packet processingunit 1804 can recognize that this address is the HoA of the MN 100 andthat the packet is a packet transmitted from the interface connected tothe home network of the MN 100.

Still moreover, as well as the aforesaid case of the HA, in the CN 150,upon receipt of a binding information notification message (includinginformation for specifying an object of replacement) for making arequest for the replacement of the home network connection informationor the CoA association information from a predetermined communicationpartner in a state where the entry of the predetermined communicationpartner is held in the binding information holding unit 1803 in advance,the binding information notification message processing unit 1802 givesan instruction to the binding information holding unit 1803 for thereplacement with the notified home network connection information or CoAassociation information.

Yet moreover, upon receipt of an instruction from the transmissionpacket generating unit 1805, the destination address selecting unit 1806conducts a selection of a destination address of a packet generated bythe transmission packet generating unit 1805. In a case in which the HoAof the MN 100 is set as the destination address of the packet generatedby the transmission packet generating unit 1805, the destination addressselecting unit 1806 retrieves the entry in which stored is the bindinginformation related to this HoA, and selects a destination address byuse of the CoA association information or home network connectioninformation held in that entry. In a case in which both the home networkconnection information and CoA association information on the MN 100 areheld in the binding information holding unit 1803, the destinationaddress selecting unit 1806 can recognize that the MN 100 is connectedto the home network and also holds the CoA associated with this HoA.Therefore, in the case of the selection of the CoA, a packet can be sentdirectly to the CoA through the use of the route optimization based onthe mobile IP while, in the case of the selection of the HoA, a packetcan be delivered directly to the interface connected to the home networkof the MN 100.

Incidentally, in a case in which the destination address selecting unit1806 utilized a function to manage a plurality of addresses notifiedfrom the MN 100 and map these addresses into an ID (address) to benotified to an upper layer, it can also play a role as an addressselecting unit for this function. Even if a mapping function exists, itcan also function as a destination address selecting unit independent ofthat function.

Moreover, when only the CoA association information is held therein, thedestination address selecting unit 1806 can recognize that the MN 100 isconnected to a foreign network and the address acquired therein isusable as a CoA. Still moreover, if only the home network connectioninformation is held therein, the destination address selecting unit 1806can recognize that the MN 100 is connected to the home network and thedirect communication using the home address is feasible. Yet moreover,if neither the home network connection information nor the CoAassociation information are held therein, the destination addressselecting unit 1806 selects the transmission addressed to the HoA. Inthis case, the transmission is made in a state where difficulty isexperienced in making a judgment on whether the MN 100 is connected tothe home network or the MN 100 is in connection with the foreign networkand the CoA association information is not registered. In such a case,in order to make clear the judgment between these cases, for example,the CN 150 can also make a request for the transmission of a bindinginformation notification message to the communication partner. Inaddition, upon receipt of the information (the aforesaid HAuse-inhibition information) from the MN 100 for making a request forinhibiting the communication through a specified HA, for example, thisHA use-inhibition information is held in the binding information holdingunit 1803 in a state associated with the corresponding CoA associationinformation, and the destination address selecting unit 1806 can alsoconduct a selection of a CoA with respect to an entry where the HAuse-inhibition information exists.

As described above, the CN 150 shown in FIG. 18 is capable of acquiringthe binding information on the MN 100 and capable of holding theinformation (home network connection information) on the connectioncondition on the MN 100 to the home network. In addition, the CoAassociation information where the address allocated to a differentinterface connected to a different network is associated as a CoA can beheld simultaneously with the home network connection information.

In consequence, for the destination address selection at thetransmission of a packet to the MN 100, the CN 150 can preferentiallyselect the transmission to the interface connected to the home networkof the MN 100. Moreover, in the base of the registration of both thein-connection information and CoA association information on the MN 100,for example, if a disconnection of the communication with the MN 100,using the HoA of the MN 100, has occurred, the CN 150 can select a CoAassociated with that HoA as a destination address and further make theswitching to the communication using the route optimization based on themobile IP, thereby enabling the prompt recovery of the communication.This also applies to the contrary case. In this case, for example, ifthe communication between the MN 100 using the CoA as a destinationaddress and the CN 150 falls into a disconnection state, by referring tothe home network connection information, it is possible to select anaddress for the transmission to the interface connected to the homenetwork, from the binding information related to that HoA. Thus,although usually there is a need to wait for a binding update message tobe transmitted from the MN 100 at the disconnection of thecommunication, by using the method described in the second embodiment ofthe present invention, it is possible to simultaneously hold theinformation on the HoA connected to the home network and the informationon the HoA associated with the CoA, which enables the switching of thedestination in a moment and minimizes the packet loss.

In addition, even in the case of using an HoA as a destination addressof a packet to be transmitted to the MN 100, as well as the routeoptimization using a CoA, the CN 150 can seize that a packet can bedelivered directly to the MN 100. In particular, in the case of thereception of a notification for the registration of the in-connectioninformation from the MN 100 in a state where the CN 150 holds aplurality of CoA association information on the MN 100, since a newlyproduced entry or entries other than the replaced entry are left intact,the CN 150 can grasp the CoA association information on the MN 100 andfurther seize the fact that the MN 100 is in connection with the homenetwork.

Even in the case of the reception of a notification for the registrationof the non-connection information from the MN 100, as well as the caseof the in-connection information, since the entries other than theregistered entry are left as they stand, the CN 150 can grasp the CoAassociation information of the MN 100 and further seize the fact thatthe MN 100 is not in connection with the home network. In addition, evenin a state where only the home network connection information isregistered, the CN 150 can distinguish between the fact that the MN 100is in connection with the home network and the fact that the MN 100 isin connection with the foreign network.

Moreover, with respect to the registered CoA association information onthe MN 100 and the home network information, if a policy for thedestination address selection or the like is appended, the reference andcomparison of the home network connection information is made to apolicy for other CoA association information, thereby enabling theaddress selection based on the policy. Even in a case in which the HA ofthe MN 100 becomes a communication partner of the MN 100, it is possibleto provide advantages similar to these in a case in which the CN 150 isa communication partner of the MN 100.

Furthermore, a brief description will be given of a concrete operationaccording to the second embodiment of the present invention. Forexample, as shown in FIG. 7, let it be assumed that, when the MN 100 isin connection with both the home network 1 and the foreign network 1,the MN 100 makes a communication with the CN 150. In this case, asmentioned above, the information shown in FIG. 9B is notified from theMN 100 through a binding information notification message to the HA1,and the HA1, which has acquired this information and which hasproxy-received a packet transmitted from the CN 150 to the HoA of the MN100, can transmit the packet not only to the interface connected to theforeign network 1 but also to the interface connected to the homenetwork 1 of the MN 100.

In addition, when the MN 100 has notified the information shown in FIG.9B to the HA1 through the use of a binding information notificationmessage, the CN 150 can select one of the HoA1 and CoA1 of the MN 100 asa destination address of a packet to be transmitted to the MN 100. Inthe case of the selection of the HoA, the packet is sent directly to theinterface connected to the home network of the MN 100. On the otherhand, in the case of the selection of the CoA, the packet is delivereddirectly to the CoA1 through the use of the route optimization based onthe mobile IP.

As described above, the HA shown in FIG. 17 and the CN 150 shown in FIG.18 can acquire the binding information (for example, information shownin FIGS. 9A to 9D) on the MN 100 and can hold the information (homenetwork connection information) on the connection information of the MN100 to the home network. In addition, it is possible to hold the CoAassociation information where the address allocated to a differentinterface connected to a different network is associated as a CoA,simultaneously with the home network connection information, and byreferring to these pieces of information, it is possible to graspwhether the MN 100 is in connection with the home network or is not inconnection therewith. If the non-connection information is registered,the HA and/or CN 150 can recognize the fact that the MN 100 cangenerate/notify further CoA association information, which can providethe basis for a request for this information to the MN 100.

Third Embodiment

Furthermore, a description will be given hereinbelow of a configurationof a network according to a third embodiment of the present invention.The third embodiment of the present invention will also be explainedusing the network configuration according to the second embodiment ofthe present invention shown in FIG. 7. The configuration of thecommunication system shown in FIG. 7 is one example, and the presentinvention is not limited to the configuration shown in FIG. 7.

In FIG. 7, there are shown three networks (home network 1 of MN 100,foreign network 1, foreign network 2), an MN 100 having two interfacesof an interface which is in connection with the home network 1 and aninterface which is in connection with the foreign network 1, and a CN150 which is in connection with the foreign network 2. Moreover, eachnetwork is connected through the internet 110, and an HA 1 which is ahome agent of the MN 100 exists in the home network 1.

The MN 100 shown in FIG. 7 has a plurality of interfaces so as to enablethe simultaneous connections with a plurality of different networks. Thetwo interfaces of the MN 100 are connected to the home network 1 and theforeign network 1. An HoA valid in the home network 1 is allocated tothe MN 100 and, in the following description, this address is referredto as HoA1. On the other hand, an address valid in the foreign network 1is allocated to the interface connected to the foreign network 1, andthis address is handled as a CoA. In the following description, thisaddress is referred to as a CoA1. The number of the interfaces held bythe MN 100 according to the third embodiment is not limited to two, andone or plurality is acceptable. Likewise, the numbers of home networksto be allocated to the MN 100, foreign networks and home agents are notlimited to the configuration shown in FIG. 7. One or plurality isacceptable.

FIG. 7 shows a case in which one of the networks with which the MN 100is in connection is a home network for the MN 100 and the other is aforeign network for the MN 100. Whether the network with which the MN100 is in connection is a home network or a foreign network depends uponthe judgment as to whether this MN 100 recognizes that network as a homenetwork or a foreign network. For example, conceivable are a method ofmaking a judgment on the basis of which of the networks is theconnection-accepting network to the MN 100, a method of making ajudgment which of the networks the MN 100 itself configures as theconnection-accepting network and a method of using a combination of boththe judgments. In the case of the former judgment method, it isconsidered that the recognition on the network by the MN 100 dependsupon the information on the home network allocated dynamically orstatically, while in the case of the latter judgment method, it isconsidered that the network recognition depends on a configuration takenby the MN 100 itself. In FIG. 7, the home network and the foreignnetwork have a configuration the MN 100 recognizes.

The third embodiment of the present invention will be describedhereinbelow in consideration of a case in which, in the networkconfiguration shown in FIG. 7, in a state where the MN 100 uses twointerfaces to establish the connections with the home network 1 and theforeign network 1 at the same time, the MN 100 makes a communicationwith the CN 150 through the use of both the interfaces.

First, a description will be given of a configuration of the MN 100according to the third embodiment of the present invention. FIG. 19 is ablock diagram showing one example of a configuration of the MN 100according to the third embodiment of the present invention. The MN 100shown in FIG. 19 is composed of a transmission/reception unit 1901, anIP address acquiring unit 1902, an allocation mobility associationinformation holding unit 1903, a connected network judging unit 1904, anotified HoA information holding unit 1905 and a binding informationnotification message generating unit 1906. In FIG. 19, althoughfunctions realized in the MN 100 are shown by blocks, these functionsare realizable by hardware or software. The transmission/reception unit1901 and the allocation mobility association information holding unit1903 are the same as the transmission/reception unit 201 and theallocation mobility association information holding unit 203,respectively, and the description thereof will be omitted.

The IP address acquiring unit 1902 fulfills a function to generate oracquire an IP address through the use of the address automatic setting(stateless address autoconfiguration), the DHCP (Dynamic HostConfiguration Protocol), the manual setting or the like for the purposeof obtaining a valid IP address in a network connected thereto.Moreover, for example, conceivable is a case in which an address isdynamically allocated from an operator side in a manner different fromthe DHCP.

In addition, the IP address acquiring unit 1902 gives an instruction tothe connected network judging unit 1904 for making a judgment as towhether the connected network is the home network or the foreignnetwork. If the judgment result by the connected network judging unit1904 shows the connection with the home network, the IP addressacquiring unit 1902 generates/acquires an address different from its ownhome address valid in that home network and allocates it to theinterface. On the other hand, if the judgment result shows theconnection with the foreign network, the IP address acquiring unit 1902generates/acquires an address valid in that foreign network andallocates it to the interface. It is also acceptable that the aforesaidaddress is generated in advance before the judgment result.

For example, in the case of the employment of the address automaticsetting, the IP address acquiring unit 1902 hands over a prefix,advertised in a connected network, to the connected network judging unit1904 to indicate the judgment on the connected network on the basis ofthis prefix. If the judgment result by the connected network judgingunit 1904 shows a connection with the home network, the IP addressacquiring unit 1902 automatically generates an address by use of aprefix acquired in advance and allocates it to the interface. However,it is necessary that the address to be generated in this case is anaddress different from the home address valid in the connected homenetwork. On the other hand, if the judgment result shows a connectionwith the foreign network, the IP address acquiring unit 1902automatically generates an address by use of the prefix previouslyacquired. An IP address acquired by the IP address acquiring unit 1902in this way is allocated to a communication interface of thetransmission/reception unit 1901 in a state associated. Incidentally,the acquisition of the prefix information on a connection-accepting sidenetwork and the address generation/acquisition method are not limited tothe above-mentioned methods.

The connected network judging unit 1904 has a function to make ajudgment on a network with which it is in connection. For example, theIP address acquiring unit 1902 uses the address automatic setting, theconnected network judging unit 1904 acquires a prefix of its own homenetwork from the allocation mobility association information holdingunit 1903 so as to make a comparison between this acquired prefix and aprefix in the connected network notified from the IP address acquiringunit 1902. When this comparison result shows that both the prefixesagree with each other, a judgment is made that it is in connection withthe home network. If they do not agree with each other, a judgment ismade that it is in connection with a foreign network. The connectednetwork judging unit 1904 hands over this judgment result (the homenetwork connection information indicative of whether or not theconnection-accepting network is the home network) to the IP addressacquiring unit 1902. Although the judgment method mentioned above ismade on the basis of the information on the home network allocated tothe MN 100, it is also possible to employ a method of making a judgmentin consideration of one of the networks to be employed by the MN 100itself. The method of making a judgment on a connected network is notlimited to the above-mentioned methods, but an arbitrary method isemployable which can detect a variation of a connected network.

In addition, the connected network judging unit 1904 hands over, to thenotified HoA information holding unit 1905, the result of the judgmenton whether the network connected to the interface of the MN 100 is thehome network or the foreign network, as the home network connectioninformation to give an instruction for the notified HoA informationholding unit 1905 to hold this information, and further hands it over tothe binding information notification message generating unit 1906 togive an instruction for the generation of a binding informationnotification message so that this information is notified to the HAand/or the CN 150.

A description will be given hereinbelow of the home network connectioninformation according to the third embodiment. In a case in which thenetwork connected to one interface is the home network, the connectednetwork judging unit 1904 of the MN 100 according to the thirdembodiment uses an address (which will be referred to hereinafter as ahome CoA), generated/acquired by the IP address acquiring unit 1902 andallocated to this interface, as the information for notifying the homenetwork connection information (in-connection information) indicative ofthe connection with the home network. Accordingly, when the judgmentshows that the connected network is the home network, the connectednetwork judging unit 1904 hands over the home CoA generated/acquired bythe IP address acquiring unit 1902 and allocated to the interface andits own HoA valid in this home network to the notified HoA informationholding unit 1905 so as to give an instruction so that the notified HoAinformation holding unit 1905 holds the association information, andhands it over to the binding information notification message generatingunit 1906 so as to give an instruction for the generation of a bindinginformation notification message so that this information (home networkconnection information) is notified to the HA and/or the CN 150.

A description will be given hereinbelow of a case in which a bindingupdate message based on the mobile IP is used as a binding informationnotification message. With respect to a method of generating a bindingupdate message for notifying a home CoA as home network connectioninformation, it is possible to employ the same method as that for thebinding update in the case of the notification of a normal CoA (whichwill be referred to hereinafter as a foreign CoA) allocated to aninterface connected to a foreign network. That is, the home CoA is setin a section of the binding update message where the foreign CoA is setin the CoA association information, which enables the home networkconnection information to be used as a binding information notificationmessage. FIG. 20 shows a binding update message in a case in which ahome CoA is set by use of an alternate CoA (alternate Care-of Address)option. In the case of this generation method, as will be mentionedlater, the HA and/or the CN 150 according to the third embodiment arerequired to have a means for making a discrimination as to whether theCoA association information included in the binding update message is aforeign CoA or a home CoA.

In addition, it is also possible that information (which will bereferred to hereinafter as home CoA inclusion information) whichexplicitly indicates the connection with the home network and the factthat the CoA association information included is a home CoA is appendedto a binding update message generated in this way. In this case, forexample, as shown in FIG. 21, a flag (which will be referred tohereinafter as a home CoA flag) is set in a CoA association informationsetting section (alternate CoA option or the like) and the flag is setfor the setting of the home CoA, which enables the inclusion of the homeCoA to be explicitly notified to a reception side node. Also in the caseof this generation method, likewise, the HA and/or the CN 150 accordingto the third embodiment are required to have a means for processing thehome CoA flag in the binding update message. With respect to the homeCoA flag setting section, in addition to the alternate CoA option, it isalso possible to provide it in a reserved field or the like in a bindingupdate message as shown in FIG. 23. Moreover, in place of the flag, itis also acceptable to employ a method in which a field (home CoA flag orhome CoA field) is provided to set a value indicative of a home CoAtherein as shown in FIGS. 21 to 24.

Still additionally, in a case in which the MN 100 appends an ID to eachinformation or a message carrying the information so that the HA and/orthe CN 150 can distinguish among a plurality of CoA associationinformation, it is also appropriate that a home CoA flag is set in anoption including this ID. In this case, there is a need for this optionto be used not only at the registration of a normal CoA but also at theregistration of a home CoA.

Yet additionally, it is also appropriate that a new option for setting ahome CoA is produced instead of the alternate CoA option and is put in abinding update message, and it is also acceptable to use an option towhich allocated is an option type different from the alternate CoAoption. Incidentally, with respect to the binding informationnotification message to the CN 150, the home CoA is not always notifiedas the information for the notification of the home network connectioninformation, but it is also acceptable to notify only the aforesaid homeCoA inclusion information as the home network connection information. Ina case in which the home CoA and/or the foreign CoA are registered inthe HA, a packet transmitted from the CN 150 to the HoA isproxy-received by the HA and transferred to the home CoA or a differentforeign CoA. In a case in which the home network connection informationis notified through the use of the home CoA flag in the alternate CoAoption, if it is found that the value included does not depict the homeCoA, the value of a portion designating the CoA association informationcan stand at an arbitrary value. For example, it is possible todesignate the HoA itself, or to specify a different value. In this case,the aforesaid home CoA inclusion information is not limited to theinformation indicative of the inclusion of the home CoA, but it merelyindicates that the home CoA inclusion information can be used as theinformation indicative of the connection with the home network and thatthe home CoA inclusion information can be handled as the home networkconnection information.

Moreover, it is also appropriate that the MN 100 puts the home CoAinclusion information in the individual alternate CoA option, the optionincluding an ID, a new option or the like and simultaneously uses a flagin the reserved field of the aforesaid binding update message. In thiscase, upon receipt of this binding update message, before checking theoption, the HA can grasp that the MN 100 has made a request for theregistration of the home network connection information or that ithandles the registration of the home network connection information.

Still moreover, in a case in which, without using the alternate CoAoption, an address set as the source address of the binding updatemessage is used as a CoA to be associated with the HoA, it is alsoacceptable to set a home CoA as the source address without setting thehome CoA in the alternate CoA option as mentioned above. In a case inwhich the home CoA inclusion information is appended, although it ispreferable that the home CoA inclusion information is placed in asection other than the alternate CoA option, in the case of theutilization of the home CoA inclusion information in the alternate CoAoption, in a section of the option where set is the CoA associationinformation, there is included a value which indicates that the value inthe section designating the CoA association information in the alternateCoA option is not used as a home CoA.

On the other hand, in a case in which the connected network judging unit1904 makes a judgment that the network connected to the interface of theMN 100 is the foreign network, the connected network judging unit 1904hands over the address (foreign CoA) allocated to the interfaceconnected to this foreign network and the HoA associated with theforeign CoA to the notified HoA information holding unit 1905 to give aninstruction thereto for holding these pieces of information, and itfurther hands over these pieces of information to the bindinginformation notification message generating unit 1906 to give aninstruction thereto so that the binding information notification messagegenerating unit 1906 generates a binding information notificationmessage for notifying these pieces of information (CoA associationinformation related to the foreign CoA) to the HA and/or the CN 150.

In addition, in a case in which the connected network judging unit 1904makes a judgment that the network connected to the interface of the MN100 is the foreign network, the connected network judging unit 1904hands over the information (non-connection information), indicating thatthe connection-accepting network is not the home network, to thenotified HoA information holding unit 1905 to give an instructionthereto for holding this information, and it further hands over thisinformation to the binding information notification message generatingunit 1906 to give an instruction thereto so that the binding informationnotification message generating unit 1906 generates a bindinginformation notification message for notifying this information to theHA and/or the CN 150.

A description will be given hereinbelow of a case in which a bindingupdate message based on the mobile IP is used as a binding informationnotification message for notifying the non-connection information as thehome network connection information. As the binding update message fornotifying the non-connection information as the home network connectioninformation, it is possible to directly use the binding update messageto be used at the notification of the foreign CoA allocated to theinterface connected to the foreign network. That is, in a case in whichthe foreign CoA is included as the CoA association information in thebinding update message for notifying the CoA association information,the processing is conducted so that the notification-receiving siderecognizes that the interface to which this foreign CoA is allocated isnot in connection with the home network. FIG. 25 is an illustration of abinding update message when a foreign CoA is set through the use of analternate CoA option.

In the case of this generation method, as will be mentioned later, theHA and/or the CN 150 according to the third embodiment is required tohave a means for distinguishing whether the CoA association informationincluded in the binding update message is the foreign CoA or the HomeCoA.

It is also possible that the information (foreign CoA inclusioninformation) explicitly indicating that the included CoA associationinformation is the foreign CoA is appended to the binding update messagegenerated by this method. In this case, for example, as shown in FIG.26, when the above-mentioned home CoA is not set at the setting of theforeign CoA, it is possible to explicitly notify, to the reception sidenode, the fact of no inclusion of the foreign CoA. Also in thisgeneration method, likewise, the HA and/or the CN 150 according to thethird embodiment is required to have a means for processing the home CoAflag in the binding update message. Moreover, it is also acceptable toemploy a method of setting a value indicative of the foreign CoA in theabove-mentioned home CoA field. Still moreover, it is also acceptablethat a foreign CoA flag similar in type to the home CoA flag is providedseparately from the home CoA flag so as to indicate that the foreign CoAis included when this flag is set. Yet moreover, it is also acceptablethat, instead of the alternate CoA option, a new option is produced forsetting a foreign CoA and is put in the binding update message, or thatit is also possible to use an option to which an option type differentfrom the alternate CoA option is allocated.

In a case in which the notification of the non-connection information isexplicitly made according to the above-mentioned method, there is noneed to put the foreign CoA serving as the CoA association informationin the binding update message. Moreover, it is also acceptable that theHoA itself is set in the portion of the CoA association information soas to set it as the binding update message for the notification of thenon-connection information, or that the foreign CoA inclusioninformation is further appended to this message.

In addition, there is no need to limit the above-mentioned foreign CoAinclusion information to the information indicative of the inclusion ofthe foreign CoA, and it is also possible to use it merely as theinformation indicative of the connection with the foreign network.

Still additionally, in a case in which, without using the alternate CoAoption, an address set as the source address of the binding updatemessage is used as a CoA associated with an HoA, the foreign CoA is notset in the alternate CoA option as mentioned above, the foreign CoA canbe set in the source address. Although it is preferable that, when thehome inclusion information is appended, it is provided in a sectionother than the alternate CoA option, in the case of the utilization ofthe home CoA inclusion information in the alternate CoA option, a valueindicating that a value in a section designating the CoA associationinformation in the alternate CoA option is not used as the foreign CoAcan be included in a section setting the CoA association information inthe alternate CoA option.

It is also acceptable that a plurality of non-connection informationeach mentioned above and a plurality of CoA association information eachmentioned above are notified simultaneously or separately. Moreover, itis also acceptable that only the information to be notified is selectedand notified. Still moreover, it is also possible that the home networkinformation (in-connection information, non-connection information) andthe CoA association information related to the normal foreign CoA arenotified simultaneously or separately as the information related to aplurality of interfaces held by the MN 100. In addition, likewise, withrespect to these pieces of information, only the information to benotified is selected and notified.

The binding information notification message generating unit 1906fulfills a function to generate a binding information notificationmessage including the home network connection information notified fromthe connected network judging unit 1904 and to hand over this bindinginformation notification message to the transmission/reception unit 1901so as to drive an instruction thereto for the transmission.

As the binding information notification message, it is also possible touse a binding update message based on the mobile IP as mentioned above,to use a message according to a different protocol, or to use a newlyproduced massage. Moreover, if the information (information includingthe in-connection information) shown in FIG. 27A or 27B can be notifiedto a destination as will be mentioned later, all formats are acceptable.The MN 100 uses the binding information notification message fornotifying, to a destination, the information for specifying an HoA whichis an object of registration, a home CoA associated with this HoA andthe information indicative of home CoA inclusion information (home CoAflag or the like). Still moreover, it is also acceptable that the MN 100notifies the information (information including the non-connectioninformation), shown in FIG. 27C or 27D and mentioned later, to adestination. Also in this case, likewise, messages with all formats areavailable.

With respect to the transmission of the home network connectioninformation, in the case of the notification of the in-connectioninformation, it is preferable that the information is transmitted whenthe MN 100 establishes a connection with its own home network or is inconnection therewith. On the other hand, in the case of the notificationof the non-connection information, it is preferable that thisinformation is transmitted when the MN 100 is not in connection with itsown home network. Moreover, it is also acceptable that the transmissionis made at the same timing as the binding update based on the mobile IP.Still moreover, the transmission of the home network connectioninformation is not always made when the MN 100 makes a connection withthe home network, it is in connection therewith and it is innon-connection therewith, but it is also acceptable that thetransmission thereof is arbitrarily made according to the judgment by auser or operator. Yet moreover, the destination of the bindinginformation notification message is not limited to the nodes (HA1 and/orCN 150) constituting the network shown in FIG. 7, but every node whichcan utilize the home network connection information and CoA associationinformation on the MN 100 are acceptable. For example, the transmissioncan be made toward a proxy node having a function to fulfill a proxy forthe HA or the CN 150, and it can also be made to a management nodehaving a function to manage the information on the MN 100.

In addition, in a case in which the CoA association information ondifferent addresses allocated to the same interface or differentinterfaces and the home network connection information are held in thenotified HoA information holding unit 1905, or when the judgment showsthat there is a need to notify this information, this information can betransmitted in a state included in the binding information notificationmessage which is for notifying the home network connection informationand the CoA association information. For example, in the case of the MN100 in the configuration shown in FIG. 7, the home network connectioninformation on the interface connected to the home network 1 and the CoAassociation information on the foreign CoA of the interface connected tothe foreign network 1 can be transmitted through the use of separatebinding information notification messages, or they can also betransmitted in a state included in a single binding informationnotification message.

Still additionally, in a case in which the MN 100 is in connection withthe foreign network 1 and the foreign network 3 like the configurationshown in FIG. 10, the CoA association information on the foreign CoA ofthe interface connected to the foreign network 1 and/or the foreignnetwork 3 and the non-connection information forming the home networkconnection information can be transmitted through the use of separatebinding information notification messages, or they can also betransmitted in a state included in a single binding informationnotification message.

The notified HoA information holding unit 1905 has a function to holdbinding information handed over from the connected network judging unit1904 and notified to the HA or the CN 150. The notified HoA informationholding unit 1905 holds, as the information the MN 100 has transmittedto its own HA or the CN 150, the CoA association information indicativeof the association between the HoA and the CoA transmitted through theuse of a normal binding update message based on the mobile IP, thein-connection indicative of the connection with the home network and thenon-connection information indicative of no connection with the homenetwork. The notified HoA information holding unit 1905 can be realizedin the form of a binding update list specified in the mobile IP, or itcan also be realized as a separate data holding unit.

Referring to FIGS. 27A, 27B, 27C and 27C, a description will be givenhereinbelow of information (home network connection information) theconnected network judging unit 1904 hands over to the notified HoAinformation holding unit 1905 and the binding information notificationmessage generating unit 1906 in the MN 100. FIGS. 27A and 27B show firstand second examples of the in-connection information the connectednetwork judging unit 1904 hands over to the notified HoA informationholding unit 1905 and the binding information notification messagegenerating unit 1906 in the MN 100 according to the third embodiment ofthe present invention.

As shown in FIG. 27A, the connected network judging unit 1904 adds, tothe HoA1 allocated to the interface connected to the home network 1, thein-connection information indicative of the fact of being currently inconnection with the home network 1 which has allocated this HoA1. Asshown in FIG. 27B, it is also possible that the information on anaddress (CoA1) allocated to a different interface is additionally addedsimultaneously as a CoA associated with the HoA1.

FIGS. 27C and 27D show first and second examples of the non-connectioninformation the connected network judging unit 1904 hands over to thenotified HoA information holding unit 1905 and the binding informationnotification message generating unit 1906 in the MN 100 according to thethird embodiment of the present invention. The information shown inFIGS. 27C and 27D signify a state in which, as shown in FIG. 10, the MN100 is in connection with the foreign network 1 and the foreign network3 and the CoA1 and the CoA 3 are allocated to the interfaces connectedto the foreign network 1 and the foreign network 3. As shown in FIG. 10,in a case in which the MN 100 is in connection with the foreign network1 and the foreign network 3 and the CoA 1 is allocated from the foreignnetwork 1 and the CoA 3 is allocated from the foreign network 3, asshown in FIG. 27C, the connected network judging unit 1904 adds, to itsown HoA1, the non-connection information indicative of the fact of beingnot currently in connection with the home network 1 which has allocatedthe HoA1. Moreover, as shown in FIG. 27D, it is also possible that theforeign CoA is put in the non-connection information. Still moreover, itis also acceptable that the information on an address (CoA3) allocatedto a different interface is added simultaneously as a CoA associatedwith the HoA1. Although the information on only the CoA1 is handled asthe non-connection information in FIG. 27D, it is also acceptable thatthe CoA 3 can also be handled as the non-connection information. Yetmoreover, it is also acceptable that, without associating the foreignCoA, the foreign CoA inclusion information is merely handled as theinformation indicative of the connection with the foreign network sothat it is taken as the non-connection information excluding the foreignCoA.

The MN 100 can transmit a binding information notification message,produced by the binding information notification message generating unit1906, to the HA and/or the CN 150 so as to notify the fact that it is inconnection with the home network and, simultaneously, notify the fact ofthe information independent of the information on the address allocatedto a different interface to the HA and/or the CN 150. In addition, theMN 100 becomes capable of notifying that it is in connection with theforeign network but not in connection with the home network. Theinformation shown in FIGS. 27A to 27D and grasped/managed by the MN 100is notified through a binding information notification message to the HAand/or the CN 150.

Incidentally, the binding information notification message is notlimited to the above-mentioned method of extending a binding updatemessage based on the mobile IP and, for example, it is also appropriatethat the information is placed in a message according to a protocolhandling the multihome before the transmission, or that a new message isproduced for carrying the information. It is also possible that theinformation is put in a plurality of HoA information notificationmessages including the information on the HA managing the HoAs, whichhas been described in the first embodiment of the present invention.

In addition, even in a case in which the MN 100, which notifies aplurality of CoA association information through the use of separatebinding update messages to a communication partner, adds an ID to eachof the binding update messages so that the communication partner candistinguish among the respective binding update messages, the MN 100 canadd such IDs to the binding update messages including the home networkconnection information. Still additionally, also when an ID is added toeach of binding information and they are transmitted through the use ofseparate binding update messages, or if a plurality of bindinginformation are transmitted with the same binding update message,likewise, such IDs can be added to the binding information including thehome network connection information. Thus, the communication partner cancarry out the registration, deletion and replacement on the basis of theIDs added.

Yet additionally, in a case in which the MN 100 notifies a policy on thedestination address selection to the CN 150, combined with the CoAassociation information, the information (home CoA or foreign CoA) to benotified as the home network connection information can also betransmitted in a state where the same type of policy is added thereto.

Moreover, it is also possible that, by transmitting a binding updatemessage for the deletion of the CoA association information on a normalforeign CoA or a binding update message for the deletion of the bindinginformation to be used as the home network connection information, aninstruction is given to a communication partner which has received thismessage so that the held entry which is an object of deletion iscorrected or replaced so as to hold new home network connectioninformation.

When the MN 100 itself transmits a packet, the MN 100 can also carry outthe source address selection using the home network connectioninformation similar to that notified to the HA and/or the CN 150. Alsoin the case of using a function to manage a plurality of addresses heldby the MN 100 itself and map these addresses into an ID (address) to benotified to an upper layer, it is possible to utilize the home networkconnection information according to the third embodiment of the presentinvention with respect to the address selection for that function. Evenif a mapping function exists, it is also possible to fulfill a functionas a destination address selecting unit independently of this function.

Moreover, in a case in which the MN 100 which is in connection with thehome network carries out the return routability specified in the mobileIP before transmitting a binding update message including the homenetwork connection information to the CN 150, the MN 100 can use a homeCoA notified as the in-connection information to the HA, as the sourceaddress of a care-of test init (CoTI) message. Still moreover, the MN100 can use the home CoA as the source address even at the encapsulationinto the HA for the transmission of a home test init (HoTI) message.That is, even in the case of the connection with the home network, it ispossible to carry out the return routability based on the mobile IP withrespect to that interface. Yet moreover, at the implementation of thereturn routability on the foreign CoA of the interface connected to theforeign network, it is also possible to encapsulate the home test initin a state where the home CoA is set as the source address and transmitit to the HA. In this case, although the care-of init test message istransmitted from the interface to which the foreign CoA is allocated,the home test init message can be transmitted from the interfaceconnected to the home network.

As described above, the MN 100 shown in FIG. 19 can notify the fact ofthe connection with the home network through the use of a bindinginformation notification message to communication nodes such as its ownHA1 and/or the CN 150. Since the information to be registered by thisnotification can exist independently of the CoA association information(the association between the HoA and the foreign CoA) on the normalforeign CoA, the MN 100 shown in FIG. 7 can notify to its own HA1 and/orthe CN 150 the fact that it is possible to directly receive packets fromboth the interface connected to the home network 1 and the interfaceconnected to the foreign network 1.

In addition, the MN 100 can notify the fact that it is in connectionwith the foreign network but not in connection with the home network. Inthis case, the MN 100 can notify to the HA1 and/or the CN 150 the factthat all packets addressed to that HoA are delivered through the HA1 tothe MN 100. Thus, even in the case of no registration of the CoAassociation information on the MN 100, the HA1 and/or the CN 150 cangrasp that the MN 100 is not in connection with the home network.

Still additionally, it is also appropriate that the MN 100 not onlynotifies the in-connection/non-connection with the home network as thehome network connection information but also notifies, as one of thehome network connection information, the information (HA use-inhibitioninformation) for making a request for the inhibition of thecommunication through the HA if some trouble has occurred in the HAmanaging the HoA or when the communication through the HA is notdesirable for other arbitrary reasons. It is preferable that a nodewhich has received this notification selects the transmission to the CoAthrough the use of the route optimization based on the mobile IP withoutselecting the HoA as the destination address.

In a case in which the MN 100 holds a plurality of HoAs (for example,HoA1 and HoA2), also when the MN 100 uses the HoA1 as an address (CoA)associated with the HoA2, it is also appropriate that the MN 100 appliesthe home network connection information (in-connection information,non-connection information) or HA use-inhibition information accordingto the third embodiment of the present invention to this address for thenotification to the HA and/or the CN 150. For example, in the case ofthe notification as the in-connection information, the in-connectioninformation on the home network is notified with respect to the HoA1 setin the section of the CoA. In this case, the in-connection informationis appended to the HoA1, and the HA and/or the CN 150 can grasp that theHoA1 of the MN 100 registered as the CoA is in connection with a validhome network and, when making the transmission in a state where thisaddress is set as the destination, they can deliver a packet directly tothe MN 100. Moreover, in a case in which the CoA section includes theHoA1 as the non-connection information, the HA and/or the CN 150 canseize the fact of no connection with the home network relative to theHoA1 of the MN 100 registered as the CoA and, when making thetransmission in a state where this address is set as the destination,they can seize that the packet is delivered through the HA to the MN100.

It is also possible that a home CoA and/or home CoA inclusioninformation are appended to the aforesaid HoA1 to be registered as theCoA. Moreover, it is also acceptable that the above-mentioned pluralityof HoAs (HoA1 and HoA2) are allocated from the same home network orallocated from different home networks. A combination thereof is alsoacceptable. In particular, in the case of the HoAs allocated from thesame home network, the MN 100 is capable of using one HoA as a home CoAfor a different HoA.

In addition, in a case in which the MN 100 uses one HoA in a stateassociated with a CoA for a different HoA, by explicitly appending theinformation indicative of the fact of the CoA being the HoA into abinding information notification message (binding update message), theHA and/or the CN 150 can recognize that the packet transmitted throughthe use of this CoA association information is transmitted to the HoA ofthe MN 100. Still additionally, in a case in which the home networkconnection information according to the present invention is appended tothe HoA serving as a CoA, the HA and/or the CN 150 can recognize whetherthe packet transmitted to the CoA is sent directly to the MN 100 or itis delivered through the HA thereto. If the home network connectioninformation according to the present invention is not appended thereto,HA and/or the CN 150 cannot make a judgment as to whether the packettransmitted to the CoA is sent directly to the MN 100 or it is deliveredthereto through the HA which manages the HoA serving as the CoA.

For example, although the HA can recognize that an encapsulated packetaddressed to the MN 100 and produced by utilizing the CoA associationinformation to which appended is the information indicative of the CoAbeing the HoA is transmitted to the HoA of the MN 100, the HA cannotmake a judgment as to whether the packet directly reaches the MN 100 orit reaches the MN 100 through a different HA. In a case in which thenon-connection information constituting the home network connectioninformation according to the present invention is appended thereto, theHA can recognize that the encapsulated packet again passes through atleast one different HA.

On the other hand, as well as the aforesaid case of the HA, the CN 150can recognize that the packet addressed to the MN 100 and produced bymeans of a routing header through the use of the CoA associationinformation to which appended is the information indicative of the CoAbeing the HoA is transmitted to the HoA of the MN 100, but it cannotmake a judgment as to whether the packet is directly delivered to the MN100 or it is sent to the MN 100 through the HA managing this HoA. If thein-connection information constituting the home network connectioninformation according to the present invention is appended thereto, theCN 150 can recognize that the packet transmitted is delivered directlyto the MN 100 connected to the home network. Thus, the HA and/or the CN150 can carry out the address selection on the basis of thisrecognition. Moreover, when the non-connection information is appendedto the HoA serving as the CoA, the HA and/or the CN 150 can recognizethat there is a possibility that a CoA associated with the HoA indicatedas the CoA exists, and they can acquire a basis for a request forfurther CoA association information to the MN 100.

Furthermore, referring to FIG. 28, a description will be givenhereinbelow of a configuration of an HA according to the thirdembodiment of the present invention. FIG. 28 is a block diagram showingone example of a configuration of an HA according to the thirdembodiment of the present invention. The HA shown in FIG. 28 is composedof a transmission/reception unit 2801, an HoA addressed packet proxyreception unit 2802, a binding information notification messageprocessing unit 2803, a binding information holding unit 2804, atransfer packet generating unit 2805, a destination address selectingunit 2806 and an encapsulated packet processing unit 2807. Thetransmission/reception unit 2801 and the HoA addressed packet proxyreception unit 2802 are the same as the transmission/reception unit 1701and the HoA addressed packet proxy reception unit 1702 in FIG. 17, andthe description thereof will be omitted. In FIG. 28, although functionsrealized in the HA are shown by blocks, these functions are realizableby hardware or software.

The binding information notification message processing unit 2803fulfills a function to conduct the processing on a binding informationnotification message received from the MN 100, and it interprets thehome network connection information included in the message to grasp thesituation of the connection of the MN 100. Upon receipt of a bindingupdate message shown in FIG. 20, the HA makes a comparison between anHoA (HoA in a home address option) which is an object of registrationand an address (address contained in an alternate CoA option) includedas the address associated with that HoA and, if the prefixes of both theaddresses are identical to each other, makes an interpretation as thismessage is a binding update message for notifying the in-connectioninformation and gives an instruction to the binding information holdingunit 2804 for storing the home network connection information shown inFIG. 27A. Instead of the comparison with the HoA which is an object ofregistration, the comparison with the prefix information managed by theHA itself can also provide the same result.

Moreover, in a case in which the home CoA inclusion information isincluded in the message as shown in FIGS. 21 to 24, it is also possiblethat, by checking the contents of the information, a judgment is madethat this message is a binding update message for notifying the homenetwork connection information and the CoA included in the message is ahome CoA or a foreign CoA, or that a judgment is made using both thecontents of the home CoA inclusion information and the result of acomparison between the CoA actually included as mentioned above and theHoA.

In a case in which, for example, the information on the old address,which has been acquired before the connection of the MN 100 with thehome network and which is to be replaced with the notified home networkconnection information or CoA association information, is included inthe binding information notification message, the binding informationnotification message processing unit 2803 gives an instruction to thebinding information holding unit 2804 so that the information on the oldaddress is replaced with the notified home network connectioninformation or CoA association information. As the information on theold address, for example, in a case in which the MN 100 transmits aplurality of binding information through the use of separate bindinginformation notification messages or when it transmits a plurality ofbinding information through the use of the same binding informationnotification message, it is possible to use the ID appended for thepurpose of distinguishing among the respective binding information.

The binding information holding unit 2804 fulfills a function to, uponreceipt of an instruction from the binding information notificationmessage processing unit 2803, store the home network connectioninformation included in the binding information notification messagereceived from the MN 100, or the CoA association information. Thebinding information holding unit 2804 holds the information indicativeof the contents similar to the aforesaid information shown in FIGS. 27Ato 27D for each MN 100. The binding information holding unit 2804 can berealized as a binding cache specified in the mobile IP, or it can alsobe realized as another data holding unit.

In addition, even in a case in which the CoA association information onthe address allocated to a different interface is included together withthe home network connection information as shown in FIG. 27B, thebinding information holding unit 2804 holds both the home networkconnection information and the CoA association information. As a methodof holding the information indicative of the connection with the homenetwork, a home CoA flag is set with respect to the binding informationincluding a home CoA so that this entry explicitly indicates thein-connection information as the home network connection information. Inthis case, although two CoA information are associated with a singleHoA1 in FIG. 27B, it is also acceptable that CoA information are held ina state associated with separate HoA1, respectively. In this case, forthe discrimination from binding information on a different normalforeign CoA, a flag can be set and held. The present invention is notlimited to the method of producing a separate entry, but it is alsopossible that, for example, new information (flag or the like)indicative of the connection with the home network is appended into theentry on the CoA association information indicative of the normalassociation between an HoA and a CoA so as to indicate that the MN 100having the HoA included in this entry is in connection with not only theforeign network but also the home network.

It is also appropriate that an entry in which held is a home CoAconstituting the home network connection information and an entry inwhich held is CoA association information on a normal foreign CoA areheld separately and the fact that these entries pertain to a specifiedMN 100 is grasped by use of unique information such as an HoA, an ID orthe like. Moreover, in a case in which IDs are appended for the purposeof distinguishing among a plurality of binding information such as thehome network connection information notified from the MN 100, CoAassociation information on a normal foreign CoA and others, it isdesirable that the information is held in a state where these IDs areassociated with the respective entries, respectively.

The transfer packet generating unit 2805 acts as a means fortransferring a packet, handed over from the HoA addressed packet proxyreception unit 2802 and addressed to the HoA of the MN 100 to the MN100. At the generation of a transfer packet, the transfer packetgenerating unit 2805 gives an instruction to the destination addressselecting unit 2806 for selecting an address designated as a destinationaddress of the transfer packet and, if the address selected by thedestination address selecting unit 2806 is a home CoA or a foreign CoA,it generates a packet encapsulated into an outer header and directed tothis address and hands over this packet to the transmission/receptionunit 2801 and gives an instruction thereto for the transmission.

The destination address selecting unit 2806 fulfills a function to, uponreceipt of an instruction from the transfer packet generating unit 2805,select an optimum address to be set as a destination address of atransfer packet. For the selection of the optimum address, thedestination address selecting unit 2806 refers to the information (forexample, the information shown in FIG. 27B) stored in the bindinginformation holding unit 2804. At this time, when the CoA associationinformation indicative of the association between normal HoA and CoA anda home CoA constituting the home network connection information and aforeign CoA are included, the destination address selecting unit 2806selects one of the information and hands it over to the transfer packetgenerating unit 2805. In a case in which the destination addressselecting unit 2806 selects the in-connection information (home CoA) asthe home network connection information, when the home CoA is set as adestination address and an encapsulated packet is transmitted, thepacket can be transmitted directly to the MN 100. In the case of theselection of the binding information on the foreign CoA, the destinationaddress is encapsulated as the foreign CoA and transmitted, therebyenabling continuous communication. In the selection of the destinationaddress, it is also appropriate that, when the transmission to the HoAis selected, the home CoA associated with this HoA is handed over as aselection result to the transfer packet generating unit 2805 so as togive an instruction for the encapsulation using this address.

In the case of utilizing a function to manage a plurality of addressesnotified from the MN 100 and map these addresses into an ID (address) tobe notified to an upper layer, the destination address selecting unit2806 can play a role as an address selecting unit for this function.Moreover, even if a mapping function exists, it can function as adestination address selecting unit independent of this function.

The encapsulated packet processing unit 2807 has a function to processan encapsulated packet addressed to the HA and transmitted thereto in acase in which the MN 100, it manages, transmits a packet to the CN 150.If binding information corresponding to the source node on the receivedencapsulated packet exists in the binding information holding unit 2804as the information on the MN 100 it manages, the decapsulationprocessing is conducted with respect to this encapsulated packet.Moreover, the encapsulated packet processing unit 2807 hands over theinner packet after the processing to the transmission/reception unit2801 and gives an instruction thereto for the transmission thereof. TheHA can recognize that the MN 100 transmits the packet by use of theinterface connected to the home network when the home CoA of the MN 100it manages is set as the source address of the encapsulated packet. Itis also possible that the MN 100 gives an instruction to the bindinginformation holding unit 2804 for holding the information indicative ofthe interface used by the MN 100 in the current communication.

Although not shown, it is also appropriate that, after the HA (forexample, the HA shown in FIG. 28) according to the present inventionreceives a binding information notification message including homenetwork connection information such as a home CoA flag from the MN 100,the HA transmits a response message thereto which includes theinformation indicative of a reception result of the home networkconnection information notification from the MN 100. In this case, thereis a need for the MN 100 receiving this response message to hold afunction for interpreting this information.

In addition, although not shown, it is also appropriate that the HAaccording to the present invention puts, in a router advertisementmessage it transmits, a flag indicating the handling with respect to afunction related to the home network connection information. In thiscase, the MN 100 receiving this message is required to have a functionfor interpreting that flag. In a case in which the flag is set in themessage, the MN 100 makes a judgment that the information related to thehome network connection information can be notified to the HA in thehome network. On the other hand, if the flag is not set in the message,the MN 100 makes a judgment that the information related to the homenetwork connection information cannot be notified to the HA in the homenetwork.

As a means for indicating the information indicative of the fact thatthe HA handles a function for the home network connection information,it is also possible to use a dynamic message such as DHCPv6 or use astatic setting means by an operator or user. Moreover, it is alsopossible that a new flag is provided in a request message of the dynamichome agent address discovery specified in the mobile IPv6 and therequest message in which the flag is set indicates a request for a listof HAs handling a function related to the home network connectioninformation. Still moreover, it is also possible that a new flag is alsoprovided in a reply message thereto so as to indicate a messageincluding a list of HAs handling a function related to the home networkconnection information.

In addition, it is also acceptable that a new flag is provided in a homeagent information option specified in the mobile IPv6 so that thesetting of this flag shows that the HA indicated by the option is an HAhandling the function related to the home network connectioninformation.

As described above, the HA shown in FIG. 28 can acquire the bindinginformation on the MN 100 and can hold the information (home networkconnection information) on the connection condition of the MN 100 to thehome network. The CoA association information in which the addressallocated to a different interface connected to another network isassociated as a foreign CoA can be held simultaneously with the homenetwork connection information.

In consequence, in the destination address selection at the packettransfer to the MN 100, the HA according to the third embodiment of thepresent invention can preferentially select the transmission to theinterface connected to the home network of the MN 100.

In addition, for example, in a case in which a disconnection ofcommunication between the MN 100 using a home CoA as the destinationaddress and the CN 150 has occurred, the HA can select a differentforeign CoA associated with the HoA and proxy-receive a packet addressedto the HoA and encapsulate the packet, whose destination address is thisHoA, with respect to the foreign CoA associated with this HoA, therebyenabling prompt recovery of the communication. Conversely, for example,in a case in which a disconnection of communication between the MN 100using a foreign CoA as the destination address and the CN 150 hasoccurred, by referring to the home network connection information, it ispossible to select an address for the transmission to the interfaceconnected to the home network, from the binding information related tothat HoA.

Thus, although, usually, there is a need to wait for a binding updatemessage to be transmitted by the MN 100 at a disconnection ofcommunication, the employment of the method described in the thirdembodiment of the present invention enables simultaneously holding thehome network connection information indicative of the connection withthe home network and the information on the HoA associated with theforeign CoA, which provides an advantage in that the destination addressselection can be conducted on the basis of this information so as toswitch the destination in a moment for minimizing the packet loss.

Even if the home CoA has been used as a destination address of a packetto be transmitted to the MN 100, was well as the route optimizationusing the foreign CoA, the HA can grasp the fact that the packet can besent directly to the MN 100. In particular, upon receipt of thenotification for the registration of the in-connection information fromthe MN 100 when the HA holds a plurality of CoA association informationon the MN 100, since a newly produced entry or entries other than thereplaced entry are left intact, the HA can grasp the CoA associationinformation on the MN 100 and the fact that the MN 100 has a home CoAand is in connection with the home network.

In addition, with respect to the destination address selection for atransfer packet addressed to the MN 100, the HA can have a policy forpreferentially selecting the transfer to the interface connected to thehome network of the MN 100. When the home network connection informationaccording to the present invention is appended to an entry of thebinding information, the HA can carry out the destination addressselection according to the aforesaid policy.

Furthermore, referring to FIG. 29, a description will be givenhereinbelow of a configuration of the CN 150 according to the thirdembodiment of the present invention. FIG. 29 is a block diagram showingone example of a configuration of a CN according to the third embodimentof the present invention. The CN 150 shown in FIG. 29 is composed of atransmission/reception unit 2901, a binding information notificationmessage processing unit 2902, a binding information holding unit 2903, areceived packet processing unit 2904, a transmission packet generatingunit 2905 and a destination address selecting unit 2906. In FIG. 29,although functions realized in the CN 150 are shown by blocks, thesefunctions are realizable by hardware or software. Thetransmission/reception unit 2901 is the same as thetransmission/reception unit 1801 of the CN 150 shown in FIG. 18, and thedescription thereof will be omitted.

The binding information notification message processing unit 2902 has afunction as the binding information notification message processing unit2803 of the HA shown in FIG. 28 and further conducts the processing whenreceiving a binding information notification message excluding the homeCoA from the MN 100. In this case, the home CoA inclusion informationincluded in the message signifies the home network connectioninformation. If the in-connection information is included as the homenetwork connection information, the binding information notificationmessage processing unit 2902 recognizes that the MN 100 is in connectionwith the home network where an HoA which is an object of registrationand which is included in the message is valid and gives an instructionso that the binding information holding unit 2903 stores the bindinginformation to which the in-connection information is appended. Even ina case in which the non-connection information is included as the homenetwork connection information, likewise, an instruction is given sothat the binding information to which the non-connection information isappended is stored in the binding information holding unit 2903.

In addition, the binding information holding unit 2903 has a function asthe binding information holding unit 2804 of the HA shown in FIG. 28 andfurther has a function to hold the home network connection informationexcluding the home CoA, handed over from the binding informationnotification message processing unit 2903. In this case, the homenetwork connection information corresponds to the contents of the homeCoA inclusion information included in the message and, when the homenetwork connection information is the in-connection information, thebinding information holding unit 2903 holds the binding information towhich the in-connection information is appended and, when the homenetwork connection information is the non-connection information, thebinding information holding unit 2903 holds the binding information towhich the non-connection information is appended.

The transmission packet generating unit 2905 generates a packet to betransmitted to a communication partner and gives an instruction to thedestination address selecting unit 2906 for carrying out the addressselection by taking into the consideration the binding information heldby the binding information holding unit 2903, thereby carrying out theprocessing (packet conversion processing or the like) on the packet onthe basis of the address selected by the destination address selectingunit 2906. If the selected address is a foreign CoA, for thetransmission of the packet addressed to the MN 100 through the use ofthe route optimization based on the mobile IP, the packet conversion ismade according to the method specified in the mobile IP and theconverted packet is handed over to the transmission/reception unit 2901.On the other hand, also in a case in which the selected address is ahome CoA, as well as the case of the foreign CoA, the packet conversionis made according to the method specified in the mobile IP and theconverted packet is handed over to the transmission/reception unit 2901.Moreover, when the selected address is an HoA and no home CoA associatedwith this HoA exists, the packet addressed to the HoA is directly handedover to the transmission/reception unit 2901 without conducting thepacket conversion. Still moreover, when the selected address is an HoAand a home CoA associated with this HoA exists, the packet conversioncan be made using this home CoA.

Thus, in a case in which the in-connection information (home CoA) isselected as the home network connection information, by generating apacket addressed to the home CoA through the use of a routing header tobe utilized in the route optimization based on the mobile IP andtransmitting it, the packet can be transmitted directly to the interfaceconnected to the home network of the MN 100. Moreover, it is alsoacceptable that, instead of the employment of the routing header, thehome CoA is set as the destination address and an encapsulated packet istransmitted. On the other hand, in the case of the selection of thebinding information on the foreign CoA, the packet can be transmitted tothe foreign CoA by means of the route optimization method based on themobile IP. If the transmission addressed to the HoA is selected in thedestination address selection, it is also possible to carry out theencapsulation by use of the home CoA.

The received packet processing unit 2904 is for processing a packetreceived from the MN 100. In a case in which the received packet is apacket converted for the route optimization based on the mobile IP, forrestoring the converted packet into the original packet, the receivedpacket processing unit 2904 checks whether or not the information on theHoA is held in the binding information holding unit 2903. If the checkshows that the CoA identical to the CoA used in the packet is held asthe CoA association information on that HoA and this CoA is registeredas the home CoA, it is possible to recognize that the received packet isa packet transmitted from the interface connected to the home network ofthe MN 100. On the other hand, when this CoA is registered as a foreignCoA, it is possible to recognize that the received packet is a packettransmitted from the interface connected to the foreign network andtransmitted through the use of the normal route optimization based onthe mobile IP.

Even if the received packet is a normal packet, the received packetprocessing unit 2094 can confirm whether or not the information on theaddress set as the source address of this packet is held in the bindinginformation holding unit 2903. If the confirmation result shows that thehome network connection information on the address is held in thebinding information holding unit 2903, the received packet processingunit 2094 can recognize that the address is the HoA of the MN 100 andthe packet is a packet transmitted from the interface connected to thehome network of the MN 100.

As well as the above-mentioned case of the HA, in a state where the CN150 holds an entry of a predetermined communication partner in thebinding information holding unit 2903 in advance, upon receipt of abinding information notification message (including information forspecifying an object of replacement) for making a request for thereplacement of the home network connection information or the CoAassociation information on the foreign CoA from the communicationpartner, the binding information notification message processing unit2902 gives an instruction to the binding information holding unit 2903for the replacement with the notified home network connectioninformation or CoA association information.

Upon receipt of an instruction from the transmission packet generatingunit 2905, the destination address selecting unit 2906 selects adestination address for a packet generated by the transmission packetgenerating unit 2905. When the destination address of the packetgenerated by the transmission packet generating unit 2905 is the HoA ofthe MN 100, the destination address selecting unit 2906 retrieves anentry in which the binding information on this HoA is stored and selectsone from the CoA association information or home network connectioninformation held in the entry. In a case in which both the home networkconnection information and CoA association information on the MN 100 areheld in the binding information holding unit 2903, the destinationaddress selecting unit 2906 can recognize that the MN 100 is inconnection with the home network and the CoA associated with this HoA isalso held therein.

Incidentally, in the case of using a function for managing a pluralityof addresses notified by the MN 100 and mapping these addresses into theIDs (addresses) to be notified to an upper layer, the destinationaddress selecting unit 2906 can play a role as an address selecting unitfor this function. Even if the mapping function exists, it can functionas a destination address selecting unit independent of this function.

In addition, with respect to the selection of a destination address of apacket to be transmitted to the MN 100, the CN 150 can hold a policy forpreferentially selecting the transmission to the interface connected tothe home network of the MN 100. When the home network connectioninformation according to the present invention is added to an entry ofthe binding information, the CN 150 can carry out the destinationaddress selection according to the aforesaid policy.

If only the CoA association information on the foreign CoA is held, thedestination address selecting unit 2906 can recognize that the MN 100 isin connection with the foreign network and the address acquired thereincan be used as a CoA. Moreover, when only the home network connectioninformation is held, the destination address selecting unit 2906 canrecognize that the MN 100 is in connection with the home network and adirect communication is feasible through the use of the interfaceconnected to the home network. Still moreover, if neither home networkconnection information nor the CoA association information are held, thetransmission to the HoA is selected. In this case, the packettransmission is made in a state where difficulty is encountered inmaking a judgment as to whether the MN 100 is connected to the homenetwork or it is in connection with the foreign network and the CoAassociation information is not registered. At this time, for makingclear which of these cases has taken place, for example, the CN 150 canissue a request for the transmission of a binding informationnotification message to the communication partner. In addition, uponreceipt of the information (the aforesaid HA use-inhibition information)on a request for inhibiting the communication through a specified HAfrom the MN 100, for example, the CN 150 holds this HA use-inhibitioninformation in the binding information holding unit 2903 in a stateassociated with the corresponding CoA association information, and thedestination address selecting unit 2906 can select a CoA with respect tothe entry where the HA use-inhibition information exists.

As described above, the CN 150 shown in FIG. 29 can acquire the bindinginformation on the MN 100 and can hold the information (home networkconnection information) on the connection status of the MN 100 to thehome network. Moreover, simultaneously with the home network connectioninformation, it can hold the CoA association information where theaddress allocated to a different interface connected to a differentnetwork is associated as a foreign CoA.

In consequence, in the destination address selection at the transmissionof a packet to the MN 100, the CN 150 can preferentially select thetransmission to the interface connected to the home network of the MN100. Moreover, when both the in-connection information and CoAassociation information on the MN 100 are registered, for example, atthe occurrence of a disconnection of communication between the CN 150and the MN 100 using the home CoA of the MN 100, the CN 150 can selectthe CoA associated with that HoA as a destination address and canachieve prompt recovery of the communication by making the switching tothe communication using the route optimization based on the mobile IP.

When recognizing a plurality of HoAs held by the MN 100, the CN 150 canpreferentially select, from these plurality of HoAs, an HoA valid in thehome network with which the MN 100 is in connection, as an address ofthe MN 100 to be used for the communication. At this time, when the homeCoA is associated with this HoA, it is possible to use the home CoA asthe destination address of a packet to be transmitted actually, throughthe use of the routing header or the encapsulation. Incidentally, the CN150 can directly transmit the packet addressed to the HoA without makinga conversion into a packet using the home CoA.

Conversely, in the case of a disconnection of communication between theMN 100 using the foreign CoA as a destination address and the CN 150 orin other cases, by referring to the home network connection information,it is possible to select an address to be transmitted to the interfaceconnected to the home network, from the binding information related tothat HoA. Thus, although usually there is a need to wait for a bindingupdate message to be transmitted from the MN 100 at the disconnection ofthe communication, by using the method described in the third embodimentof the present invention, it is possible to simultaneously hold the homenetwork connection information indicative of the connection with thehome network and the information on the HoA associated with the foreignCoA, which provides an advantage of enabling the switching of thedestination in a moment by carrying out the destination addressselection on the basis of this information, thereby minimizing thepacket loss.

In addition, even in a case in which the HoA is used as a destinationaddress of a packet to be transmitted to the MN 100, as well as theroute optimization using the CoA, the CN 150 can grasp the fact that thepacket can be directly sent to the interface connected to the homenetwork of the MN 100. In particular, in a case in which the CN 150holds a plurality of CoA association information on the MN 100, when theCN 150 receives a notification for the registration of the in-connectioninformation from the MN 100, a newly produced entry or the entries otherthan the replaced entry are left intact, the CN 150 can grasp the CoAassociation information on the MN 100 and the fact that the MN 100 is inconnection with the home network.

Still additionally, even in a case in which the CN 150 receives anotification for the registration of the non-connection information fromthe MN 100, as well as the case of the in-connection information, sincethe entries other than the registered entry are left intact, the CN 150can seize the CoA association information on the MN 100 and the factthat the MN 100 is not in connection with the home network. Yetadditionally, even in a state where only the home network connectioninformation is registered, the CN 150 can make discrimination as towhether the MN 100 is in connection with the home network or it is inconnection with the foreign network.

Moreover, in a case in which a policy for the destination addressselection or the like is appended with respect to the CoA associationinformation on the foreign CoA of the MN 100 registered and the homenetwork connection information, by making reference to and making acomparison with the home network connection information together with apolicy of another CoA association information, it is possible to carryout the address selection based on the policy. Even if the HA of the MN100 is a communication partner of the MN 100, it is possible to providethe advantages similar to those in a case in which the aforesaid CN 150is a communication partner of the MN 100.

Furthermore, a brief description will be given hereinbelow of a concreteoperation according to the third embodiment of the present invention.For example, as shown in FIG. 7, let it be assumed that, when the MN 100is in connection with both the home network 1 and the foreign network 1,the MN 100 makes a communication with the CN 150. In this case, asmentioned above, the information shown in FIG. 27B is notified from theMN 100 through a binding information notification message to the HA1,and the HA1, which has acquired this information and which hasproxy-received a packet transmitted from the CN 150 to the HoA of the MN100, transmits the packet not only to the interface connected to theforeign network 1 but also to the interface connected to the home CoA,which enables it to be also transmitted to the interface connected tothe home network 1 of the MN 100.

In addition, in a case in which the MN 100 notifies, to the CN 150, theinformation shown in FIG. 27B through the use of a binding informationnotification message, the CN 150 can select one of the HoA1, home CoAand CoA1 of the MN 100 as a destination address of a packet to betransmitted to the MN 100. When the HoA1 or the home CoA is selected,the packet is directly delivered to the interface connected to the homenetwork of the MN 100. On the other hand, in the case of the selectionof the CoA1, the packet is sent directly to the CoA1 through the use ofthe route optimization based on the mobile IP.

As described above, the HA shown in FIG. 28 and the CN 150 shown in FIG.29 can acquire the binding information (for example, information shownin FIGS. 27A to 27D) on the MN 100 and can hold the information (homenetwork connection information) on the connection status of the MN 100to the home network. Moreover, they can hold the CoA associationinformation, where the address allocated to a different interfaceconnected to another network is associated as a foreign CoA,simultaneously with the home network connection information and, byreferring to this information, they can see the state as to whether theMN 100 is in connection with the home network or is not in connectiontherewith so as to carry out the destination address selection on thebasis of this information. Moreover, when the non-connection informationis registered, the HA and/or the CN 150 can recognize the fact that theMN 100 can generate/notify further CoA association information, whichprovides a basis for a request for this information to the MN 100.

Furthermore, with respect to the home network connection informationdescribed in the embodiments of the present invention, a descriptionwill be given hereinbelow of an example of an operation by taking intoconsideration a connection mode before the movement of the MN 100holding two interfaces (IF1 and IF2). In this case, let it be assumedthat the MN 100 has an HoA allocated from a home network and the twointerfaces are connectable to one of the home network and a foreignnetwork.

Operation Example 1

First, a description will be given of an operation example 1. The IF1 ofthe MN 100 is in connection with the home network, and a home CoAgenerated in the home network is registered in an HA as a transferdestination of a packet addressed to an HoA and the in-connectioninformation constituting the home network connection information isappended to the home CoA. Moreover, the IF2 is in connection with aforeign network, and a normal CoA is registered as binding informationrelative to the HoA. Although the following description will be given onthe basis of a method of using the home CoA as a transfer destination,if the HA can conduct a direct transfer to the MN 100 with the HoA beingset as a destination without employing the method using the home CoA, itis also possible to use this method, or it is also acceptable to realizethe packet transfer to the HoA by means of a combination of thesemethods. In a case in which the HA employs the method of carrying outthe direct transfer in a state where the HoA is set as a destination, itis preferable that the in-connection information is appended to the HoA.

In the above-mentioned connection state, if the IF1 connected to thehome network is switched to be connected to the foreign network, the MN100 transmits a message for deleting the in-connection information onthe IF1 and the home CoA registered as a transfer destination of apacket addressed to the HoA. At this time, the normal CoAgenerated/acquired in the foreign network is registered as a transferdestination of a packet addressed to a new HoA on the IF1.

On the other hand, in the above-mentioned connection state, if the IF2connected to the foreign network is switched to be connected to the homenetwork, the MN 100 registers the in-connection information as the homenetwork connection information on the IF2 in the HA. At this time, thehome CoA generated/acquired in the home network is registered as atransfer destination of a packet addressed to the HoA. Thus, since boththe interfaces of the MN 100 after the movement are connected to thesame home network and the in-connection information is registered withrespect to each of the interfaces, the HA can grasp the fact that the MN100 registers the two interfaces in the HoA as a transfer destination ofa packet addressed to the HoA and both the interfaces are in connectionwith the home network.

Operation Example 2

Secondly, a description will be given of an operation example 2. Boththe IF1 and IF2 are connected to the home network and home CoAsgenerated/acquired in the home network are registered as transferdestinations of a packet addressed to an HoA with respect to therespective interfaces and the in-connection information constituting thehome network connection information is appended to both the home CoAs.

In the above-mentioned connection status, when the IF1 is switched to beconnected to the foreign network, the MN 100 transmits a message fordeleting the in-connection information on the IF1 and the home CoAregistered as the transfer destination of the packet addressed to theHoA. At this time, a normal CoA generated/acquired in the foreignnetwork is registered as a transfer destination of a packet directed toa new HoA on the IF1.

On the other hand, in the above-mentioned connection status, when theIF2 is switched to be connected to the foreign network, likewise, the MN100 transmits a message for deleting the in-connection information onthe IF2 and the home CoA registered as the transfer destination of thepacket addressed to the HoA1, and a normal CoA is registered as atransfer destination of a packet directed to a new HoA on the IF2.

Operation Example 3

Furthermore, a description will be given of an operation example 3. Boththe IF1 and IF2 are connected to the foreign network, and normal CoAsare registered as transfer destinations of packets directed to HoAs onthe IF1 and the IF2 with respect to the HA.

In the above-mentioned connection status, when the IF1 is switched to beconnected to the home network, the MN 100 registers a home CoA,generated/acquired in the home network, in the HA as a new transferdestination of a packet directed to the HoA, and appends thein-connection information constituting the home network connectioninformation thereto.

On the other hand, in the above-mentioned connection status, when theIF2 is switched to be connected to the home network, likewise, the MN100 registers the in-connection information on the IF2 and a home CoA asa new transfer destination of a packet directed to the HoA.

As described above, the MN 100 becomes capable of notifying the homenetwork connection information according to a network with which eachinterface is in connection and, by registering the home CoA, becomescapable of designating a transfer destination of a packet directed tothe HoA which has been proxy-received by the HA. Incidentally, even in acase in which the MN 100 utilizes three or more interfaces, each of theinterfaces can carry out the processing similar to those in theabove-mentioned cases. That is, in a case in which the interfaceconnected to the home network exists among the interfaces of the MN 100and this interface is used as a transfer destination of a packetaddressed to the HoA, the home network connection information isnotified as the information on that IF.

In a case in which the HA employs a method of making a comparisonbetween the HoA which is an object of registration and the CoA includedas an address associated with the HoA so that, when the prefixes of boththe addresses (HoA and CoA) are the same as each other, aninterpretation is made as this message is a message for notifying thein-connection information, in the operation in the above-mentioned caseusing the home CoA, there is no need for the MN 100 to append thein-connection information on the interface connected to the home networkand, on the basis of a result of the comparison between the prefixes bythe HA, a judgment is made as to whether or not it is in connection withthe home network.

In addition, it is also appropriate that an MN switches a home networkconnection information notification method according to a handlingsituation of an HA and a situation of the MN. Conversely, it is alsoacceptable that the HA switches a home network connection informationprocessing method and a method of transferring a packet addressed to anHoA to the MN which is a transfer destination according to the handlingsituation of the MN. For example, in the case of the utilization of twointerfaces or in the case of taking into consideration an overhead forthe generation/acquisition of a home CoA, it is possible to employ amethod in which an HoA is allocated to one interface and a neighborcache related to this HoA is registered in only the HA while a CoA or ahome CoA is allocated to the other interface and this address isassociated with the HoA. In the case of the employment of this method,when the HA transfers a packet addressed to the HoA, it proxy-receives,to the interface connected to the home network of the MN 100, the HAtransfers the packet intact without carrying out the encapsulation.

Still additionally, although the in-connection information to benotified by the MN 100 is valid information in a case in which theinterface in a state connected and the other interface aresimultaneously used with respect to the HoA valid in the home network ina state connected, as mentioned below, in a case in which a plurality ofaddresses are usable in the home network, it is effectively available.

If there is an interface connected to a home network (site multihomednetwork) where a plurality of different prefixes are valid, the MN 100allocates its own HoA to this interface and further allocates anaddress, generated/acquired using a prefix other than the prefix used inthis HoA, to a different interface. Following this, the MN 100associates this address as a CoA with the HoA and further appends thein-connection information to both the HoA and CoA and registers them ina CN.

In the case of normal binding information to which no in-connectioninformation is appended, the CN makes a judgment that the addressregistered as a CoA is an address in a foreign network while, when thein-connection information is appended thereto, the CN can recognize thatboth the addresses of the HoA and CoA are addresses allocated to theinterfaces connected to the home network where the HoA is valid and,hence, it can grasp an accurate connection status of the MN 100.Moreover, the CN can selectively use the HoA and the CoA as adestination of a packet to be transmitted to the MN 100 on the basis ofthe connection status of the MN 100 so as to switch the ISP throughwhich the packet passes, which enables providing the site multihomeeffect.

In addition, in the above-mentioned case of the simultaneous employmentof the interface connected to the home network where a plurality ofdifferent prefixes are valid and a different interface, the MN 100generates home CoAs by using prefixes including the prefix used in theHoA with respect to the interface connected to the home network andappends the in-connection information to the respective home CoAs beforeregistering them. This is for registering the address of a differentinterface as a CoA in the HA, with the same information being registeredin the CN. Incidentally, without notifying, to the HA, all the home CoAsgenerated using the prefixes in the home network, it is also acceptableto notify one of the home CoAs thereto.

The contents described in the first to third embodiments of the presentinvention are also applicable to the NEMO (Network Mobility) which is atechnology for realizing the mobile transparency of a network. In thiscase, as well as the case of the MN mentioned above, the home networkconnection information on a mobile router (MR) can be notified to an HAand/or a CN, and the HA and/or the CN are capable of holding thereceived home network connection information in a manner similar to theabove-mentioned method for the MN. The HA and/or the CM according to theNEMO hold, as information on a prefix managed by the MR, information(for example, HoA) which enables specifying the MR relative to thisprefix in a state associated and, hence, as well as a case of specifyingthe CoA association information on the MR associated with the prefix,they can specify the home network connection information on the MRassociated with the prefix. It is also appropriate that the home networkconnection information is held separately from the information, which isfor specifying a different MR, in a state associated with the prefixitself, or that the home network connection information is appended toan entry on the prefix information already associated with theinformation specifying the MR and held in this state. In this case,without referring to the CoA association information on the MR, it ispossible to specify the home network connection information on the MR byonly referring to the prefix.

Furthermore, the contents described in the first to third embodiments ofthe present invention are also applicable to the MIPv4 (IP MobilitySupport for IPv4) constituting the mobile IP handling the IPv4, and theyare also applicable to a case of the utilization of the FMIP (FastHandovers for Mobile IPv6) or HMIP (Hierarchical Mobile IPv6 mobilitymanagement).

The respective functional blocks used in the above description of thefirst and third embodiments of the present invention are typicallyrealized with an LSI (Large Scale Integration) which is an integratedcircuit. It is also acceptable that these functional blocks areindividually formed as one chip, or that a portion of or all of thesefunctional blocks are formed as one chip. Although an LSI is taken inthis case, it is sometimes referred to as an IC (Integrated Circuit),system LSI, super LSI or ultra LSI according to the level ofintegration.

Moreover, the technique for the formation of an integrated circuit isnot limited to the LSI, but it is also realizable with a dedicatedcircuit or a general-purpose processor. After the manufacturing of theLSI, it is also acceptable to utilize an FPGA (Field Programmable GateArray) which enables the programming or a reconfigurable processor whichallows the reconfiguration of connections and setting of circuit cellsin the interior of the LSI.

Still moreover, if a technique for the formation of an integratedcircuit replaceable with the LSI appears owing to advance insemiconductor technology or a different technology derived therefrom,the functional blocks can naturally be integrated through the use ofthis technique. For example, a biotechnology or the like may beapplicable.

INDUSTRIAL APPLICABILITY

According to the present invention, an MN has one or a plurality of HoAsand notifies a status of connection with a network, corresponding to theone HoA or each of the plurality of HoAs, to an HA and/or a CN, whichprovides an advantage of enabling the HA and/or the CN to select anappropriate destination address. Even in a case in which an MN has aplurality of HoAs and several HoAs of these HoAs are managed by the sameHA, it is possible to provide an advantage of enabling the HA and/or theCN to select an appropriate HoA and the CN to make an efficient inquiryat the HA by notifying appropriate information to the HA and/or the CN.The present invention is applicable to a technique related tocommunication using the IP and to a technique for realizing both themultihome function and mobile function.

1. A communication node comprising: a receiver, which, in operation,receives a binding update message generated by a mobile node that has aplurality of communication interfaces operable to connect to a homenetwork and a foreign network, the binding update message including amobility option with a flag and with a care-of address field in thebinding update message set to a home address of the mobile node, whileat least one of said plurality of communication interfaces is to beadditionally connected to the home network when another communicationinterface is already connected to the foreign network; and atransmitter, which, in operation, transmits a packet to the mobile node,wherein the transmitter sets the home address as a destination addressof the packet when the received binding update message includes themobility option with the flag and with the care-of address field in thebinding update message set to the home address of the mobile node. 2.The communication node according to claim 1, wherein the mobility optionincludes a binding identifier that identifies a binding indicated by thebinding update message.
 3. The communication node according to claim 1,wherein the binding update message further includes an address assignedto the communication interface already connected to the foreign network.4. The communication node according to claim 1, wherein thecommunication node is a home agent of the mobile node.
 5. Acommunication method performed by a communication node, thecommunication method comprising the steps of: receiving a binding updatemessage generated by a mobile node that has a plurality of communicationinterfaces operable to connect to a home network and a foreign network,the binding update message including a mobility option with a flag andwith a care-of address field in the binding update message set to a homeaddress of the mobile node, while at least one of said plurality ofcommunication interfaces is to be additionally connected to the homenetwork when another communication interface is already connected to theforeign network; and transmitting a packet to the mobile node, whereinthe communication node sets the home address as a destination address ofthe packet when the received binding update message includes themobility option with the flag and with the care-of address field in thebinding update message set to the home address of the mobile node. 6.The communication method according to claim 5, wherein the mobilityoption includes a binding identifier that identifies a binding indicatedby the binding update message.
 7. The communication method according toclaim 5, wherein the binding update message further includes an addressassigned to the communication interface already connected to the foreignnetwork.
 8. The communication method according to claim 5, wherein thecommunication node is a home agent of the mobile node.